xref: /external/chromium_org/chrome/browser/extensions/extension_service.cc

// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "chrome/browser/extensions/extension_service.h"

#include <algorithm>
#include <iterator>
#include <set>

#include "base/command_line.h"
#include "base/metrics/histogram.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/stringprintf.h"
#include "base/strings/utf_string_conversions.h"
#include "base/threading/sequenced_worker_pool.h"
#include "base/threading/thread_restrictions.h"
#include "base/time/time.h"
#include "chrome/browser/browser_process.h"
#include "chrome/browser/chrome_notification_types.h"
#include "chrome/browser/content_settings/content_settings_custom_extension_provider.h"
#include "chrome/browser/content_settings/content_settings_internal_extension_provider.h"
#include "chrome/browser/content_settings/host_content_settings_map.h"
#include "chrome/browser/extensions/api/content_settings/content_settings_service.h"
#include "chrome/browser/extensions/component_loader.h"
#include "chrome/browser/extensions/crx_installer.h"
#include "chrome/browser/extensions/data_deleter.h"
#include "chrome/browser/extensions/extension_action_storage_manager.h"
#include "chrome/browser/extensions/extension_assets_manager.h"
#include "chrome/browser/extensions/extension_disabled_ui.h"
#include "chrome/browser/extensions/extension_error_controller.h"
#include "chrome/browser/extensions/extension_install_ui.h"
#include "chrome/browser/extensions/extension_special_storage_policy.h"
#include "chrome/browser/extensions/extension_sync_service.h"
#include "chrome/browser/extensions/extension_util.h"
#include "chrome/browser/extensions/external_install_manager.h"
#include "chrome/browser/extensions/external_provider_impl.h"
#include "chrome/browser/extensions/install_verifier.h"
#include "chrome/browser/extensions/installed_loader.h"
#include "chrome/browser/extensions/pending_extension_manager.h"
#include "chrome/browser/extensions/permissions_updater.h"
#include "chrome/browser/extensions/shared_module_service.h"
#include "chrome/browser/extensions/unpacked_installer.h"
#include "chrome/browser/extensions/updater/chrome_extension_downloader_factory.h"
#include "chrome/browser/extensions/updater/extension_cache.h"
#include "chrome/browser/extensions/updater/extension_downloader.h"
#include "chrome/browser/extensions/updater/extension_updater.h"
#include "chrome/browser/google/google_brand.h"
#include "chrome/browser/profiles/profile.h"
#include "chrome/browser/ui/webui/extensions/extension_icon_source.h"
#include "chrome/browser/ui/webui/favicon_source.h"
#include "chrome/browser/ui/webui/ntp/thumbnail_source.h"
#include "chrome/browser/ui/webui/theme_source.h"
#include "chrome/common/chrome_switches.h"
#include "chrome/common/crash_keys.h"
#include "chrome/common/extensions/extension_constants.h"
#include "chrome/common/extensions/features/feature_channel.h"
#include "chrome/common/extensions/manifest_url_handler.h"
#include "chrome/common/url_constants.h"
#include "components/crx_file/id_util.h"
#include "components/startup_metric_utils/startup_metric_utils.h"
#include "content/public/browser/devtools_agent_host.h"
#include "content/public/browser/notification_service.h"
#include "content/public/browser/render_process_host.h"
#include "content/public/browser/storage_partition.h"
#include "extensions/browser/event_router.h"
#include "extensions/browser/extension_host.h"
#include "extensions/browser/extension_prefs.h"
#include "extensions/browser/extension_registry.h"
#include "extensions/browser/extension_system.h"
#include "extensions/browser/install_flag.h"
#include "extensions/browser/runtime_data.h"
#include "extensions/browser/uninstall_reason.h"
#include "extensions/browser/update_observer.h"
#include "extensions/common/extension_messages.h"
#include "extensions/common/extension_urls.h"
#include "extensions/common/feature_switch.h"
#include "extensions/common/file_util.h"
#include "extensions/common/manifest_constants.h"
#include "extensions/common/manifest_handlers/background_info.h"
#include "extensions/common/one_shot_event.h"
#include "extensions/common/permissions/permission_message_provider.h"
#include "extensions/common/permissions/permissions_data.h"

#if defined(OS_CHROMEOS)
#include "chrome/browser/chromeos/extensions/install_limiter.h"
#include "storage/browser/fileapi/file_system_backend.h"
#include "storage/browser/fileapi/file_system_context.h"
#endif

using content::BrowserContext;
using content::BrowserThread;
using content::DevToolsAgentHost;
using extensions::CrxInstaller;
using extensions::Extension;
using extensions::ExtensionIdSet;
using extensions::ExtensionInfo;
using extensions::ExtensionRegistry;
using extensions::ExtensionSet;
using extensions::FeatureSwitch;
using extensions::InstallVerifier;
using extensions::ManagementPolicy;
using extensions::Manifest;
using extensions::PermissionMessage;
using extensions::PermissionMessages;
using extensions::PermissionSet;
using extensions::SharedModuleInfo;
using extensions::SharedModuleService;
using extensions::UnloadedExtensionInfo;

namespace errors = extensions::manifest_errors;

namespace {

// Wait this many seconds after an extensions becomes idle before updating it.
const int kUpdateIdleDelay = 5;

}  // namespace

// ExtensionService.

void ExtensionService::CheckExternalUninstall(const std::string& id) {
  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  // Check if the providers know about this extension.
  extensions::ProviderCollection::const_iterator i;
  for (i = external_extension_providers_.begin();
       i != external_extension_providers_.end(); ++i) {
    DCHECK(i->get()->IsReady());
    if (i->get()->HasExtension(id))
      return;  // Yup, known extension, don't uninstall.
  }

  // We get the list of external extensions to check from preferences.
  // It is possible that an extension has preferences but is not loaded.
  // For example, an extension that requires experimental permissions
  // will not be loaded if the experimental command line flag is not used.
  // In this case, do not uninstall.
  if (!GetInstalledExtension(id)) {
    // We can't call UninstallExtension with an unloaded/invalid
    // extension ID.
    LOG(WARNING) << "Attempted uninstallation of unloaded/invalid extension "
                 << "with id: " << id;
    return;
  }
  UninstallExtension(id,
                     extensions::UNINSTALL_REASON_ORPHANED_EXTERNAL_EXTENSION,
                     base::Bind(&base::DoNothing),
                     NULL);
}

void ExtensionService::SetFileTaskRunnerForTesting(
    const scoped_refptr<base::SequencedTaskRunner>& task_runner) {
  file_task_runner_ = task_runner;
}

void ExtensionService::ClearProvidersForTesting() {
  external_extension_providers_.clear();
}

void ExtensionService::AddProviderForTesting(
    extensions::ExternalProviderInterface* test_provider) {
  CHECK(test_provider);
  external_extension_providers_.push_back(
      linked_ptr<extensions::ExternalProviderInterface>(test_provider));
}

void ExtensionService::BlacklistExtensionForTest(
    const std::string& extension_id) {
  ExtensionIdSet blocked;
  ExtensionIdSet unchanged;
  blocked.insert(extension_id);
  UpdateBlockedExtensions(blocked, unchanged);
}

bool ExtensionService::OnExternalExtensionUpdateUrlFound(
    const std::string& id,
    const std::string& install_parameter,
    const GURL& update_url,
    Manifest::Location location,
    int creation_flags,
    bool mark_acknowledged) {
  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  CHECK(crx_file::id_util::IdIsValid(id));

  if (Manifest::IsExternalLocation(location)) {
    // All extensions that are not user specific can be cached.
    extensions::ExtensionCache::GetInstance()->AllowCaching(id);
  }

  const Extension* extension = GetExtensionById(id, true);
  if (extension) {
    // Already installed. Skip this install if the current location has
    // higher priority than |location|.
    Manifest::Location current = extension->location();
    if (current == Manifest::GetHigherPriorityLocation(current, location))
      return false;
    // Otherwise, overwrite the current installation.
  }

  // Add |id| to the set of pending extensions.  If it can not be added,
  // then there is already a pending record from a higher-priority install
  // source.  In this case, signal that this extension will not be
  // installed by returning false.
  if (!pending_extension_manager()->AddFromExternalUpdateUrl(
          id,
          install_parameter,
          update_url,
          location,
          creation_flags,
          mark_acknowledged)) {
    return false;
  }

  update_once_all_providers_are_ready_ = true;
  return true;
}

// static
// This function is used to uninstall an extension via sync.  The LOG statements
// within this function are used to inform the user if the uninstall cannot be
// done.
bool ExtensionService::UninstallExtensionHelper(
    ExtensionService* extensions_service,
    const std::string& extension_id,
    extensions::UninstallReason reason) {
  // We can't call UninstallExtension with an invalid extension ID.
  if (!extensions_service->GetInstalledExtension(extension_id)) {
    LOG(WARNING) << "Attempted uninstallation of non-existent extension with "
                 << "id: " << extension_id;
    return false;
  }

  // The following call to UninstallExtension will not allow an uninstall of a
  // policy-controlled extension.
  base::string16 error;
  if (!extensions_service->UninstallExtension(
          extension_id, reason, base::Bind(&base::DoNothing), &error)) {
    LOG(WARNING) << "Cannot uninstall extension with id " << extension_id
                 << ": " << error;
    return false;
  }

  return true;
}

ExtensionService::ExtensionService(Profile* profile,
                                   const CommandLine* command_line,
                                   const base::FilePath& install_directory,
                                   extensions::ExtensionPrefs* extension_prefs,
                                   extensions::Blacklist* blacklist,
                                   bool autoupdate_enabled,
                                   bool extensions_enabled,
                                   extensions::OneShotEvent* ready)
    : extensions::Blacklist::Observer(blacklist),
      profile_(profile),
      system_(extensions::ExtensionSystem::Get(profile)),
      extension_prefs_(extension_prefs),
      blacklist_(blacklist),
      extension_sync_service_(NULL),
      registry_(extensions::ExtensionRegistry::Get(profile)),
      pending_extension_manager_(profile),
      install_directory_(install_directory),
      extensions_enabled_(extensions_enabled),
      show_extensions_prompts_(true),
      install_updates_when_idle_(true),
      ready_(ready),
      update_once_all_providers_are_ready_(false),
      browser_terminating_(false),
      installs_delayed_for_gc_(false),
      is_first_run_(false),
      shared_module_service_(new extensions::SharedModuleService(profile_)) {
  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  // Figure out if extension installation should be enabled.
  if (extensions::ExtensionsBrowserClient::Get()->AreExtensionsDisabled(
          *command_line, profile))
    extensions_enabled_ = false;

  registrar_.Add(this, chrome::NOTIFICATION_APP_TERMINATING,
                 content::NotificationService::AllBrowserContextsAndSources());
  registrar_.Add(this,
                 extensions::NOTIFICATION_EXTENSION_PROCESS_TERMINATED,
                 content::NotificationService::AllBrowserContextsAndSources());
  registrar_.Add(this, content::NOTIFICATION_RENDERER_PROCESS_TERMINATED,
                 content::NotificationService::AllBrowserContextsAndSources());
  registrar_.Add(this, chrome::NOTIFICATION_UPGRADE_RECOMMENDED,
                 content::NotificationService::AllBrowserContextsAndSources());
  registrar_.Add(this,
                 chrome::NOTIFICATION_PROFILE_DESTRUCTION_STARTED,
                 content::Source<Profile>(profile_));

  extensions::ExtensionManagementFactory::GetForBrowserContext(profile_)
      ->AddObserver(this);

  // Set up the ExtensionUpdater
  if (autoupdate_enabled) {
    int update_frequency = extensions::kDefaultUpdateFrequencySeconds;
    if (command_line->HasSwitch(switches::kExtensionsUpdateFrequency)) {
      base::StringToInt(command_line->GetSwitchValueASCII(
          switches::kExtensionsUpdateFrequency),
          &update_frequency);
    }
    updater_.reset(new extensions::ExtensionUpdater(
        this,
        extension_prefs,
        profile->GetPrefs(),
        profile,
        update_frequency,
        extensions::ExtensionCache::GetInstance(),
        base::Bind(ChromeExtensionDownloaderFactory::CreateForProfile,
                   profile)));
  }

  component_loader_.reset(
      new extensions::ComponentLoader(this,
                                      profile->GetPrefs(),
                                      g_browser_process->local_state(),
                                      profile));

  if (extensions_enabled_) {
    extensions::ExternalProviderImpl::CreateExternalProviders(
        this, profile_, &external_extension_providers_);
  }

  // Set this as the ExtensionService for app sorting to ensure it causes syncs
  // if required.
  is_first_run_ = !extension_prefs_->SetAlertSystemFirstRun();

  error_controller_.reset(
      new extensions::ExtensionErrorController(profile_, is_first_run_));
  external_install_manager_.reset(
      new extensions::ExternalInstallManager(profile_, is_first_run_));

  extension_action_storage_manager_.reset(
      new extensions::ExtensionActionStorageManager(profile_));

  // How long is the path to the Extensions directory?
  UMA_HISTOGRAM_CUSTOM_COUNTS("Extensions.ExtensionRootPathLength",
                              install_directory_.value().length(), 0, 500, 100);
}

const ExtensionSet* ExtensionService::extensions() const {
  return &registry_->enabled_extensions();
}

extensions::PendingExtensionManager*
    ExtensionService::pending_extension_manager() {
  return &pending_extension_manager_;
}

ExtensionService::~ExtensionService() {
  // No need to unload extensions here because they are profile-scoped, and the
  // profile is in the process of being deleted.

  extensions::ProviderCollection::const_iterator i;
  for (i = external_extension_providers_.begin();
       i != external_extension_providers_.end(); ++i) {
    extensions::ExternalProviderInterface* provider = i->get();
    provider->ServiceShutdown();
  }
}

void ExtensionService::Shutdown() {
  extensions::ExtensionManagementFactory::GetInstance()
      ->GetForBrowserContext(profile())
      ->RemoveObserver(this);
  system_->management_policy()->UnregisterProvider(
      shared_module_policy_provider_.get());
}

const Extension* ExtensionService::GetExtensionById(
    const std::string& id, bool include_disabled) const {
  int include_mask = ExtensionRegistry::ENABLED;
  if (include_disabled) {
    // Include blacklisted extensions here because there are hundreds of
    // callers of this function, and many might assume that this includes those
    // that have been disabled due to blacklisting.
    include_mask |= ExtensionRegistry::DISABLED |
                    ExtensionRegistry::BLACKLISTED;
  }
  return registry_->GetExtensionById(id, include_mask);
}

void ExtensionService::Init() {
  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  base::Time begin_time = base::Time::Now();

  DCHECK(!is_ready());  // Can't redo init.
  DCHECK_EQ(registry_->enabled_extensions().size(), 0u);

  const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
  if (cmd_line->HasSwitch(switches::kInstallEphemeralAppFromWebstore)) {
    // The sole purpose of this launch is to install a new extension from CWS
    // and immediately terminate: loading already installed extensions is
    // unnecessary and may interfere with the inline install dialog (e.g. if an
    // extension listens to onStartup and opens a window).
    SetReadyAndNotifyListeners();
  } else {
    // LoadAllExtensions() calls OnLoadedInstalledExtensions().
    component_loader_->LoadAll();
    extensions::InstalledLoader(this).LoadAllExtensions();

    // Attempt to re-enable extensions whose only disable reason is reloading.
    std::vector<std::string> extensions_to_enable;
    const ExtensionSet& disabled_extensions = registry_->disabled_extensions();
    for (ExtensionSet::const_iterator iter = disabled_extensions.begin();
        iter != disabled_extensions.end(); ++iter) {
      const Extension* e = iter->get();
      if (extension_prefs_->GetDisableReasons(e->id()) ==
          Extension::DISABLE_RELOAD) {
        extensions_to_enable.push_back(e->id());
      }
    }
    for (std::vector<std::string>::iterator it = extensions_to_enable.begin();
         it != extensions_to_enable.end(); ++it) {
      EnableExtension(*it);
    }

    // Finish install (if possible) of extensions that were still delayed while
    // the browser was shut down.
    scoped_ptr<extensions::ExtensionPrefs::ExtensionsInfo> delayed_info(
        extension_prefs_->GetAllDelayedInstallInfo());
    for (size_t i = 0; i < delayed_info->size(); ++i) {
      ExtensionInfo* info = delayed_info->at(i).get();
      scoped_refptr<const Extension> extension(NULL);
      if (info->extension_manifest) {
        std::string error;
        extension = Extension::Create(
            info->extension_path,
            info->extension_location,
            *info->extension_manifest,
            extension_prefs_->GetDelayedInstallCreationFlags(
                info->extension_id),
            info->extension_id,
            &error);
        if (extension.get())
          delayed_installs_.Insert(extension);
      }
    }
    MaybeFinishDelayedInstallations();

    scoped_ptr<extensions::ExtensionPrefs::ExtensionsInfo> delayed_info2(
        extension_prefs_->GetAllDelayedInstallInfo());
    UMA_HISTOGRAM_COUNTS_100("Extensions.UpdateOnLoad",
                             delayed_info2->size() - delayed_info->size());

    SetReadyAndNotifyListeners();

    // TODO(erikkay) this should probably be deferred to a future point
    // rather than running immediately at startup.
    CheckForExternalUpdates();

    LoadGreylistFromPrefs();
  }

  UMA_HISTOGRAM_TIMES("Extensions.ExtensionServiceInitTime",
                      base::Time::Now() - begin_time);
}

void ExtensionService::LoadGreylistFromPrefs() {
  scoped_ptr<ExtensionSet> all_extensions =
      registry_->GenerateInstalledExtensionsSet();

  for (ExtensionSet::const_iterator it = all_extensions->begin();
       it != all_extensions->end(); ++it) {
    extensions::BlacklistState state =
        extension_prefs_->GetExtensionBlacklistState((*it)->id());
    if (state == extensions::BLACKLISTED_SECURITY_VULNERABILITY ||
        state == extensions::BLACKLISTED_POTENTIALLY_UNWANTED ||
        state == extensions::BLACKLISTED_CWS_POLICY_VIOLATION)
      greylist_.Insert(*it);
  }
}

bool ExtensionService::UpdateExtension(const std::string& id,
                                       const base::FilePath& extension_path,
                                       bool file_ownership_passed,
                                       CrxInstaller** out_crx_installer) {
  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  if (browser_terminating_) {
    LOG(WARNING) << "Skipping UpdateExtension due to browser shutdown";
    // Leak the temp file at extension_path. We don't want to add to the disk
    // I/O burden at shutdown, we can't rely on the I/O completing anyway, and
    // the file is in the OS temp directory which should be cleaned up for us.
    return false;
  }

  const extensions::PendingExtensionInfo* pending_extension_info =
      pending_extension_manager()->GetById(id);

  const Extension* extension = GetInstalledExtension(id);
  if (!pending_extension_info && !extension) {
    LOG(WARNING) << "Will not update extension " << id
                 << " because it is not installed or pending";
    // Delete extension_path since we're not creating a CrxInstaller
    // that would do it for us.
    if (!GetFileTaskRunner()->PostTask(
            FROM_HERE,
            base::Bind(
                &extensions::file_util::DeleteFile, extension_path, false)))
      NOTREACHED();

    return false;
  }

  // We want a silent install only for non-pending extensions and
  // pending extensions that have install_silently set.
  scoped_ptr<ExtensionInstallPrompt> client;
  if (pending_extension_info && !pending_extension_info->install_silently())
    client.reset(ExtensionInstallUI::CreateInstallPromptWithProfile(profile_));

  scoped_refptr<CrxInstaller> installer(
      CrxInstaller::Create(this, client.Pass()));
  installer->set_expected_id(id);
  int creation_flags = Extension::NO_FLAGS;
  if (pending_extension_info) {
    installer->set_install_source(pending_extension_info->install_source());
    if (pending_extension_info->install_silently())
      installer->set_allow_silent_install(true);
    if (pending_extension_info->remote_install())
      installer->set_grant_permissions(false);
    creation_flags = pending_extension_info->creation_flags();
    if (pending_extension_info->mark_acknowledged())
      external_install_manager_->AcknowledgeExternalExtension(id);
  } else if (extension) {
    installer->set_install_source(extension->location());
  }
  // If the extension was installed from or has migrated to the webstore, or
  // its auto-update URL is from the webstore, treat it as a webstore install.
  // Note that we ignore some older extensions with blank auto-update URLs
  // because we are mostly concerned with restrictions on NaCl extensions,
  // which are newer.
  if ((extension && extension->from_webstore()) ||
      (extension && extensions::ManifestURL::UpdatesFromGallery(extension)) ||
      (!extension && extension_urls::IsWebstoreUpdateUrl(
           pending_extension_info->update_url()))) {
    creation_flags |= Extension::FROM_WEBSTORE;
  }

  // Bookmark apps being updated is kind of a contradiction, but that's because
  // we mark the default apps as bookmark apps, and they're hosted in the web
  // store, thus they can get updated. See http://crbug.com/101605 for more
  // details.
  if (extension && extension->from_bookmark())
    creation_flags |= Extension::FROM_BOOKMARK;

  if (extension && extension->was_installed_by_default())
    creation_flags |= Extension::WAS_INSTALLED_BY_DEFAULT;

  if (extension && extension->was_installed_by_oem())
    creation_flags |= Extension::WAS_INSTALLED_BY_OEM;

  if (extension && extension->was_installed_by_custodian())
    creation_flags |= Extension::WAS_INSTALLED_BY_CUSTODIAN;

  if (extension) {
    installer->set_is_ephemeral(extension_prefs_->IsEphemeralApp(id));
    installer->set_do_not_sync(extension_prefs_->DoNotSync(id));
  }

  installer->set_creation_flags(creation_flags);

  installer->set_delete_source(file_ownership_passed);
  installer->set_install_cause(extension_misc::INSTALL_CAUSE_UPDATE);
  installer->InstallCrx(extension_path);

  if (out_crx_installer)
    *out_crx_installer = installer.get();

  return true;
}

void ExtensionService::ReloadExtensionImpl(
    // "transient" because the process of reloading may cause the reference
    // to become invalid. Instead, use |extension_id|, a copy.
    const std::string& transient_extension_id,
    bool be_noisy) {
  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  // If the extension is already reloading, don't reload again.
  if (extension_prefs_->GetDisableReasons(transient_extension_id) &
      Extension::DISABLE_RELOAD) {
    return;
  }

  // Ignore attempts to reload a blacklisted extension. Sometimes this can
  // happen in a convoluted reload sequence triggered by the termination of a
  // blacklisted extension and a naive attempt to reload it. For an example see
  // http://crbug.com/373842.
  if (registry_->blacklisted_extensions().Contains(transient_extension_id))
    return;

  base::FilePath path;

  std::string extension_id = transient_extension_id;
  const Extension* transient_current_extension =
      GetExtensionById(extension_id, false);

  // Disable the extension if it's loaded. It might not be loaded if it crashed.
  if (transient_current_extension) {
    // If the extension has an inspector open for its background page, detach
    // the inspector and hang onto a cookie for it, so that we can reattach
    // later.
    // TODO(yoz): this is not incognito-safe!
    extensions::ProcessManager* manager = system_->process_manager();
    extensions::ExtensionHost* host =
        manager->GetBackgroundHostForExtension(extension_id);
    if (host && DevToolsAgentHost::HasFor(host->host_contents())) {
      // Look for an open inspector for the background page.
      scoped_refptr<DevToolsAgentHost> agent_host =
          DevToolsAgentHost::GetOrCreateFor(host->host_contents());
      agent_host->DisconnectWebContents();
      orphaned_dev_tools_[extension_id] = agent_host;
    }

    path = transient_current_extension->path();
    // BeingUpgraded is set back to false when the extension is added.
    system_->runtime_data()->SetBeingUpgraded(transient_current_extension,
                                              true);
    DisableExtension(extension_id, Extension::DISABLE_RELOAD);
    reloading_extensions_.insert(extension_id);
  } else {
    std::map<std::string, base::FilePath>::const_iterator iter =
        unloaded_extension_paths_.find(extension_id);
    if (iter == unloaded_extension_paths_.end()) {
      return;
    }
    path = unloaded_extension_paths_[extension_id];
  }

  transient_current_extension = NULL;

  if (delayed_installs_.Contains(extension_id)) {
    FinishDelayedInstallation(extension_id);
    return;
  }

  // If we're reloading a component extension, use the component extension
  // loader's reloader.
  if (component_loader_->Exists(extension_id)) {
    component_loader_->Reload(extension_id);
    return;
  }

  // Check the installed extensions to see if what we're reloading was already
  // installed.
  scoped_ptr<ExtensionInfo> installed_extension(
      extension_prefs_->GetInstalledExtensionInfo(extension_id));
  if (installed_extension.get() &&
      installed_extension->extension_manifest.get()) {
    extensions::InstalledLoader(this).Load(*installed_extension, false);
  } else {
    // Otherwise, the extension is unpacked (location LOAD).
    // We should always be able to remember the extension's path. If it's not in
    // the map, someone failed to update |unloaded_extension_paths_|.
    CHECK(!path.empty());
    scoped_refptr<extensions::UnpackedInstaller> unpacked_installer =
        extensions::UnpackedInstaller::Create(this);
    unpacked_installer->set_be_noisy_on_failure(be_noisy);
    unpacked_installer->Load(path);
  }
}

void ExtensionService::ReloadExtension(const std::string& extension_id) {
  ReloadExtensionImpl(extension_id, true); // be_noisy
}

void ExtensionService::ReloadExtensionWithQuietFailure(
    const std::string& extension_id) {
  ReloadExtensionImpl(extension_id, false); // be_noisy
}

bool ExtensionService::UninstallExtension(
    // "transient" because the process of uninstalling may cause the reference
    // to become invalid. Instead, use |extenson->id()|.
    const std::string& transient_extension_id,
    extensions::UninstallReason reason,
    const base::Closure& deletion_done_callback,
    base::string16* error) {
  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  scoped_refptr<const Extension> extension =
      GetInstalledExtension(transient_extension_id);

  // Callers should not send us nonexistent extensions.
  CHECK(extension.get());

  // Policy change which triggers an uninstall will always set
  // |external_uninstall| to true so this is the only way to uninstall
  // managed extensions.
  // Shared modules being uninstalled will also set |external_uninstall| to true
  // so that we can guarantee users don't uninstall a shared module.
  // (crbug.com/273300)
  // TODO(rdevlin.cronin): This is probably not right. We should do something
  // else, like include an enum IS_INTERNAL_UNINSTALL or IS_USER_UNINSTALL so
  // we don't do this.
  bool external_uninstall =
      (reason == extensions::UNINSTALL_REASON_INTERNAL_MANAGEMENT) ||
      (reason == extensions::UNINSTALL_REASON_REINSTALL) ||
      (reason == extensions::UNINSTALL_REASON_ORPHANED_EXTERNAL_EXTENSION) ||
      (reason == extensions::UNINSTALL_REASON_ORPHANED_SHARED_MODULE) ||
      (reason == extensions::UNINSTALL_REASON_SYNC &&
           extension->was_installed_by_custodian());
  if (!external_uninstall &&
      !system_->management_policy()->UserMayModifySettings(
        extension.get(), error)) {
    content::NotificationService::current()->Notify(
        extensions::NOTIFICATION_EXTENSION_UNINSTALL_NOT_ALLOWED,
        content::Source<Profile>(profile_),
        content::Details<const Extension>(extension.get()));
    return false;
  }

  syncer::SyncChange sync_change;
  // Don't sync the uninstall if we're going to reinstall the extension
  // momentarily.
  if (extension_sync_service_ &&
      reason != extensions::UNINSTALL_REASON_REINSTALL) {
     sync_change = extension_sync_service_->PrepareToSyncUninstallExtension(
        extension.get(), is_ready());
  }

  system_->install_verifier()->Remove(extension->id());

  UMA_HISTOGRAM_ENUMERATION("Extensions.UninstallType",
                            extension->GetType(), 100);
  RecordPermissionMessagesHistogram(extension.get(),
                                    "Extensions.Permissions_Uninstall2");

  // Unload before doing more cleanup to ensure that nothing is hanging on to
  // any of these resources.
  UnloadExtension(extension->id(), UnloadedExtensionInfo::REASON_UNINSTALL);

  // Tell the backend to start deleting installed extensions on the file thread.
  if (!Manifest::IsUnpackedLocation(extension->location())) {
    if (!GetFileTaskRunner()->PostTask(
            FROM_HERE,
            base::Bind(&ExtensionService::UninstallExtensionOnFileThread,
                       extension->id(),
                       profile_,
                       install_directory_,
                       extension->path())))
      NOTREACHED();
  }

  extensions::DataDeleter::StartDeleting(
      profile_, extension.get(), deletion_done_callback);

  UntrackTerminatedExtension(extension->id());

  // Notify interested parties that we've uninstalled this extension.
  content::NotificationService::current()->Notify(
      extensions::NOTIFICATION_EXTENSION_UNINSTALLED_DEPRECATED,
      content::Source<Profile>(profile_),
      content::Details<const Extension>(extension.get()));
  ExtensionRegistry::Get(profile_)
      ->TriggerOnUninstalled(extension.get(), reason);

  if (sync_change.IsValid()) {
    extension_sync_service_->ProcessSyncUninstallExtension(extension->id(),
                                                           sync_change);
  }

  delayed_installs_.Remove(extension->id());

  extension_prefs_->OnExtensionUninstalled(
      extension->id(), extension->location(), external_uninstall);

  // Track the uninstallation.
  UMA_HISTOGRAM_ENUMERATION("Extensions.ExtensionUninstalled", 1, 2);

  return true;
}

// static
void ExtensionService::UninstallExtensionOnFileThread(
    const std::string& id,
    Profile* profile,
    const base::FilePath& install_dir,
    const base::FilePath& extension_path) {
  extensions::ExtensionAssetsManager* assets_manager =
      extensions::ExtensionAssetsManager::GetInstance();
  assets_manager->UninstallExtension(id, profile, install_dir, extension_path);
}

bool ExtensionService::IsExtensionEnabled(
    const std::string& extension_id) const {
  if (registry_->enabled_extensions().Contains(extension_id) ||
      registry_->terminated_extensions().Contains(extension_id)) {
    return true;
  }

  if (registry_->disabled_extensions().Contains(extension_id) ||
      registry_->blacklisted_extensions().Contains(extension_id)) {
    return false;
  }

  // If the extension hasn't been loaded yet, check the prefs for it. Assume
  // enabled unless otherwise noted.
  return !extension_prefs_->IsExtensionDisabled(extension_id) &&
         !extension_prefs_->IsExtensionBlacklisted(extension_id) &&
         !extension_prefs_->IsExternalExtensionUninstalled(extension_id);
}

void ExtensionService::EnableExtension(const std::string& extension_id) {
  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  if (IsExtensionEnabled(extension_id))
    return;
  const Extension* extension =
      registry_->disabled_extensions().GetByID(extension_id);

  ManagementPolicy* policy = system_->management_policy();
  if (extension && policy->MustRemainDisabled(extension, NULL, NULL)) {
    UMA_HISTOGRAM_COUNTS_100("Extensions.EnableDeniedByPolicy", 1);
    return;
  }

  extension_prefs_->SetExtensionState(extension_id, Extension::ENABLED);
  extension_prefs_->ClearDisableReasons(extension_id);

  // This can happen if sync enables an extension that is not
  // installed yet.
  if (!extension)
    return;

  // Move it over to the enabled list.
  registry_->AddEnabled(make_scoped_refptr(extension));
  registry_->RemoveDisabled(extension->id());

  NotifyExtensionLoaded(extension);

  // Notify listeners that the extension was enabled.
  content::NotificationService::current()->Notify(
      extensions::NOTIFICATION_EXTENSION_ENABLED,
      content::Source<Profile>(profile_),
      content::Details<const Extension>(extension));

  if (extension_sync_service_)
    extension_sync_service_->SyncEnableExtension(*extension);
}

void ExtensionService::DisableExtension(
    const std::string& extension_id,
    Extension::DisableReason disable_reason) {
  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  // The extension may have been disabled already. Just add a disable reason.
  if (!IsExtensionEnabled(extension_id)) {
    extension_prefs_->AddDisableReason(extension_id, disable_reason);
    return;
  }

  const Extension* extension = GetInstalledExtension(extension_id);
  // |extension| can be NULL if sync disables an extension that is not
  // installed yet.
  // EXTERNAL_COMPONENT extensions are not generally modifiable by users, but
  // can be uninstalled by the browser if the user sets extension-specific
  // preferences.
  if (extension &&
      disable_reason != Extension::DISABLE_RELOAD &&
      !system_->management_policy()->UserMayModifySettings(extension, NULL) &&
      extension->location() != Manifest::EXTERNAL_COMPONENT) {
    return;
  }

  extension_prefs_->SetExtensionState(extension_id, Extension::DISABLED);
  extension_prefs_->AddDisableReason(extension_id, disable_reason);

  int include_mask =
      ExtensionRegistry::EVERYTHING & ~ExtensionRegistry::DISABLED;
  extension = registry_->GetExtensionById(extension_id, include_mask);
  if (!extension)
    return;

  // The extension is either enabled or terminated.
  DCHECK(registry_->enabled_extensions().Contains(extension->id()) ||
         registry_->terminated_extensions().Contains(extension->id()));

  // Move it over to the disabled list. Don't send a second unload notification
  // for terminated extensions being disabled.
  registry_->AddDisabled(make_scoped_refptr(extension));
  if (registry_->enabled_extensions().Contains(extension->id())) {
    registry_->RemoveEnabled(extension->id());
    NotifyExtensionUnloaded(extension, UnloadedExtensionInfo::REASON_DISABLE);
  } else {
    registry_->RemoveTerminated(extension->id());
  }

  if (extension_sync_service_)
    extension_sync_service_->SyncDisableExtension(*extension);
}

void ExtensionService::DisableUserExtensions(
    const std::vector<std::string>& except_ids) {
  extensions::ManagementPolicy* management_policy =
      system_->management_policy();
  extensions::ExtensionList to_disable;

  const ExtensionSet& enabled_set = registry_->enabled_extensions();
  for (ExtensionSet::const_iterator extension = enabled_set.begin();
      extension != enabled_set.end(); ++extension) {
    if (management_policy->UserMayModifySettings(extension->get(), NULL))
      to_disable.push_back(*extension);
  }
  const ExtensionSet& terminated_set = registry_->terminated_extensions();
  for (ExtensionSet::const_iterator extension = terminated_set.begin();
      extension != terminated_set.end(); ++extension) {
    if (management_policy->UserMayModifySettings(extension->get(), NULL))
      to_disable.push_back(*extension);
  }

  for (extensions::ExtensionList::const_iterator extension = to_disable.begin();
      extension != to_disable.end(); ++extension) {
    if ((*extension)->was_installed_by_default() &&
        extension_urls::IsWebstoreUpdateUrl(
            extensions::ManifestURL::GetUpdateURL(extension->get())))
      continue;
    const std::string& id = (*extension)->id();
    if (except_ids.end() == std::find(except_ids.begin(), except_ids.end(), id))
      DisableExtension(id, extensions::Extension::DISABLE_USER_ACTION);
  }
}

void ExtensionService::GrantPermissionsAndEnableExtension(
    const Extension* extension) {
  GrantPermissions(extension);
  RecordPermissionMessagesHistogram(extension,
                                    "Extensions.Permissions_ReEnable2");
  extension_prefs_->SetDidExtensionEscalatePermissions(extension, false);
  EnableExtension(extension->id());
}

void ExtensionService::GrantPermissions(const Extension* extension) {
  CHECK(extension);
  extensions::PermissionsUpdater(profile()).GrantActivePermissions(extension);
}

// static
void ExtensionService::RecordPermissionMessagesHistogram(
    const Extension* extension, const char* histogram) {
  // Since this is called from multiple sources, and since the histogram macros
  // use statics, we need to manually lookup the histogram ourselves.
  base::HistogramBase* counter = base::LinearHistogram::FactoryGet(
      histogram,
      1,
      PermissionMessage::kEnumBoundary,
      PermissionMessage::kEnumBoundary + 1,
      base::HistogramBase::kUmaTargetedHistogramFlag);

  PermissionMessages permissions =
      extension->permissions_data()->GetPermissionMessages();
  if (permissions.empty()) {
    counter->Add(PermissionMessage::kNone);
  } else {
    for (PermissionMessages::iterator it = permissions.begin();
         it != permissions.end(); ++it)