xref: /external/chromium_org/chrome/browser/prerender/prerender_contents.cc

// Copyright (c) 2012 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/prerender/prerender_contents.h"

#include <algorithm>
#include <functional>
#include <utility>

#include "base/strings/utf_string_conversions.h"
#include "chrome/browser/chrome_notification_types.h"
#include "chrome/browser/favicon/favicon_tab_helper.h"
#include "chrome/browser/history/history_tab_helper.h"
#include "chrome/browser/history/history_types.h"
#include "chrome/browser/prerender/prerender_field_trial.h"
#include "chrome/browser/prerender/prerender_final_status.h"
#include "chrome/browser/prerender/prerender_handle.h"
#include "chrome/browser/prerender/prerender_manager.h"
#include "chrome/browser/prerender/prerender_render_view_host_observer.h"
#include "chrome/browser/prerender/prerender_tracker.h"
#include "chrome/browser/profiles/profile.h"
#include "chrome/browser/ui/browser.h"
#include "chrome/browser/ui/browser_tab_contents.h"
#include "chrome/common/prerender_messages.h"
#include "chrome/common/url_constants.h"
#include "content/public/browser/browser_child_process_host.h"
#include "content/public/browser/notification_service.h"
#include "content/public/browser/render_process_host.h"
#include "content/public/browser/render_view_host.h"
#include "content/public/browser/resource_request_details.h"
#include "content/public/browser/session_storage_namespace.h"
#include "content/public/browser/web_contents.h"
#include "content/public/browser/web_contents_delegate.h"
#include "content/public/browser/web_contents_view.h"
#include "content/public/common/favicon_url.h"
#include "ui/gfx/rect.h"

using content::DownloadItem;
using content::OpenURLParams;
using content::RenderViewHost;
using content::ResourceRedirectDetails;
using content::SessionStorageNamespace;
using content::WebContents;

namespace prerender {

class PrerenderContentsFactoryImpl : public PrerenderContents::Factory {
 public:
  virtual PrerenderContents* CreatePrerenderContents(
      PrerenderManager* prerender_manager, Profile* profile,
      const GURL& url, const content::Referrer& referrer,
      Origin origin, uint8 experiment_id) OVERRIDE {
    return new PrerenderContents(prerender_manager, profile,
                                 url, referrer, origin, experiment_id);
  }
};

// WebContentsDelegateImpl -----------------------------------------------------

class PrerenderContents::WebContentsDelegateImpl
    : public content::WebContentsDelegate {
 public:
  explicit WebContentsDelegateImpl(PrerenderContents* prerender_contents)
      : prerender_contents_(prerender_contents) {
  }

  // content::WebContentsDelegate implementation:
  virtual WebContents* OpenURLFromTab(WebContents* source,
                                      const OpenURLParams& params) OVERRIDE {
    // |OpenURLFromTab| is typically called when a frame performs a navigation
    // that requires the browser to perform the transition instead of WebKit.
    // Examples include prerendering a site that redirects to an app URL,
    // or if --enable-strict-site-isolation is specified and the prerendered
    // frame redirects to a different origin.
    // TODO(cbentzel): Consider supporting this if it is a common case during
    // prerenders.
    prerender_contents_->Destroy(FINAL_STATUS_OPEN_URL);
    return NULL;
  }

  virtual void CanDownload(
      RenderViewHost* render_view_host,
      int request_id,
      const std::string& request_method,
      const base::Callback<void(bool)>& callback) OVERRIDE {
    prerender_contents_->Destroy(FINAL_STATUS_DOWNLOAD);
    // Cancel the download.
    callback.Run(false);
  }

  virtual bool ShouldCreateWebContents(
      WebContents* web_contents,
      int route_id,
      WindowContainerType window_container_type,
      const string16& frame_name,
      const GURL& target_url,
      const content::Referrer& referrer,
      WindowOpenDisposition disposition,
      const WebKit::WebWindowFeatures& features,
      bool user_gesture,
      bool opener_suppressed) OVERRIDE {
    // Since we don't want to permit child windows that would have a
    // window.opener property, terminate prerendering.
    prerender_contents_->Destroy(FINAL_STATUS_CREATE_NEW_WINDOW);
    // Cancel the popup.
    return false;
  }

  virtual bool OnGoToEntryOffset(int offset) OVERRIDE {
    // This isn't allowed because the history merge operation
    // does not work if there are renderer issued challenges.
    // TODO(cbentzel): Cancel in this case? May not need to do
    // since render-issued offset navigations are not guaranteed,
    // but indicates that the page cares about the history.
    return false;
  }

  virtual void JSOutOfMemory(WebContents* tab) OVERRIDE {
    prerender_contents_->Destroy(FINAL_STATUS_JS_OUT_OF_MEMORY);
  }

  virtual bool ShouldSuppressDialogs() OVERRIDE {
    // We still want to show the user the message when they navigate to this
    // page, so cancel this prerender.
    prerender_contents_->Destroy(FINAL_STATUS_JAVASCRIPT_ALERT);
    // Always suppress JavaScript messages if they're triggered by a page being
    // prerendered.
    return true;
  }

  virtual void RegisterProtocolHandler(WebContents* web_contents,
                                       const std::string& protocol,
                                       const GURL& url,
                                       const string16& title,
                                       bool user_gesture) OVERRIDE {
    // TODO(mmenke): Consider supporting this if it is a common case during
    // prerenders.
    prerender_contents_->Destroy(FINAL_STATUS_REGISTER_PROTOCOL_HANDLER);
  }

 private:
  PrerenderContents* prerender_contents_;
};

void PrerenderContents::Observer::OnPrerenderStopLoading(
    PrerenderContents* contents) {
}

void PrerenderContents::Observer::OnPrerenderCreatedMatchCompleteReplacement(
    PrerenderContents* contents, PrerenderContents* replacement) {
}

PrerenderContents::Observer::Observer() {
}

PrerenderContents::Observer::~Observer() {
}

PrerenderContents::PendingPrerenderInfo::PendingPrerenderInfo(
    base::WeakPtr<PrerenderHandle> weak_prerender_handle,
    Origin origin,
    const GURL& url,
    const content::Referrer& referrer,
    const gfx::Size& size)
    : weak_prerender_handle(weak_prerender_handle),
      origin(origin),
      url(url),
      referrer(referrer),
      size(size) {
}

PrerenderContents::PendingPrerenderInfo::~PendingPrerenderInfo() {
}

void PrerenderContents::AddPendingPrerender(
    scoped_ptr<PendingPrerenderInfo> pending_prerender_info) {
  pending_prerenders_.push_back(pending_prerender_info.release());
}

void PrerenderContents::PrepareForUse() {
  NotifyPrerenderStop();

  SessionStorageNamespace* session_storage_namespace = NULL;
  if (prerender_contents_) {
    // TODO(ajwong): This does not correctly handle storage for isolated apps.
    session_storage_namespace = prerender_contents_->
        GetController().GetDefaultSessionStorageNamespace();
  }
  prerender_manager_->StartPendingPrerenders(
      child_id_, &pending_prerenders_, session_storage_namespace);
  pending_prerenders_.clear();
}

PrerenderContents::PrerenderContents(
    PrerenderManager* prerender_manager,
    Profile* profile,
    const GURL& url,
    const content::Referrer& referrer,
    Origin origin,
    uint8 experiment_id)
    : prerendering_has_started_(false),
      prerender_manager_(prerender_manager),
      prerender_url_(url),
      referrer_(referrer),
      profile_(profile),
      page_id_(0),
      session_storage_namespace_id_(-1),
      has_stopped_loading_(false),
      has_finished_loading_(false),
      final_status_(FINAL_STATUS_MAX),
      match_complete_status_(MATCH_COMPLETE_DEFAULT),
      prerendering_has_been_cancelled_(false),
      child_id_(-1),
      route_id_(-1),
      origin_(origin),
      experiment_id_(experiment_id),
      creator_child_id_(-1) {
  DCHECK(prerender_manager != NULL);
}

PrerenderContents* PrerenderContents::CreateMatchCompleteReplacement() {
  PrerenderContents* new_contents = prerender_manager_->CreatePrerenderContents(
      prerender_url(), referrer(), origin(), experiment_id());

  new_contents->load_start_time_ = load_start_time_;
  new_contents->session_storage_namespace_id_ = session_storage_namespace_id_;
  new_contents->set_match_complete_status(
      PrerenderContents::MATCH_COMPLETE_REPLACEMENT_PENDING);

  const bool did_init = new_contents->Init();
  DCHECK(did_init);
  DCHECK_EQ(alias_urls_.front(), new_contents->alias_urls_.front());
  DCHECK_EQ(1u, new_contents->alias_urls_.size());
  new_contents->alias_urls_ = alias_urls_;
  new_contents->set_match_complete_status(
      PrerenderContents::MATCH_COMPLETE_REPLACEMENT);
  NotifyPrerenderCreatedMatchCompleteReplacement(new_contents);
  return new_contents;
}

bool PrerenderContents::Init() {
  return AddAliasURL(prerender_url_);
}

// static
PrerenderContents::Factory* PrerenderContents::CreateFactory() {
  return new PrerenderContentsFactoryImpl();
}

void PrerenderContents::StartPrerendering(
    int creator_child_id,
    const gfx::Size& size,
    SessionStorageNamespace* session_storage_namespace) {
  DCHECK(profile_ != NULL);
  DCHECK(!size.IsEmpty());
  DCHECK(!prerendering_has_started_);
  DCHECK(prerender_contents_.get() == NULL);
  DCHECK_EQ(-1, creator_child_id_);
  DCHECK(size_.IsEmpty());
  DCHECK_EQ(1U, alias_urls_.size());

  creator_child_id_ = creator_child_id;
  session_storage_namespace_id_ = session_storage_namespace->id();
  size_ = size;

  DCHECK(load_start_time_.is_null());
  load_start_time_ = base::TimeTicks::Now();

  // Everything after this point sets up the WebContents object and associated
  // RenderView for the prerender page. Don't do this for members of the
  // control group.
  if (prerender_manager_->IsControlGroup(experiment_id()))
    return;

  if (origin_ == ORIGIN_LOCAL_PREDICTOR &&
      IsLocalPredictorPrerenderAlwaysControlEnabled()) {
    return;
  }

  prerendering_has_started_ = true;

  prerender_contents_.reset(CreateWebContents(session_storage_namespace));
  BrowserTabContents::AttachTabHelpers(prerender_contents_.get());
#if defined(OS_ANDROID)
  // Delay icon fetching until the contents are getting swapped in
  // to conserve network usage in mobile devices.
  FaviconTabHelper::FromWebContents(
      prerender_contents_.get())->set_should_fetch_icons(false);
#endif  // defined(OS_ANDROID)
  content::WebContentsObserver::Observe(prerender_contents_.get());

  web_contents_delegate_.reset(new WebContentsDelegateImpl(this));
  prerender_contents_.get()->SetDelegate(web_contents_delegate_.get());
  // Set the size of the prerender WebContents.
  prerender_contents_->GetView()->SizeContents(size_);

  // Register as an observer of the RenderViewHost so we get messages.
  render_view_host_observer_.reset(
      new PrerenderRenderViewHostObserver(this, GetRenderViewHostMutable()));

  child_id_ = GetRenderViewHost()->GetProcess()->GetID();
  route_id_ = GetRenderViewHost()->GetRoutingID();

  // Register this with the ResourceDispatcherHost as a prerender
  // RenderViewHost. This must be done before the Navigate message to catch all
  // resource requests, but as it is on the same thread as the Navigate message
  // (IO) there is no race condition.
  AddObserver(prerender_manager()->prerender_tracker());
  NotifyPrerenderStart();

  // Close ourselves when the application is shutting down.
  notification_registrar_.Add(this, chrome::NOTIFICATION_APP_TERMINATING,
                              content::NotificationService::AllSources());

  // Register for our parent profile to shutdown, so we can shut ourselves down
  // as well (should only be called for OTR profiles, as we should receive
  // APP_TERMINATING before non-OTR profiles are destroyed).
  // TODO(tburkard): figure out if this is needed.
  notification_registrar_.Add(this, chrome::NOTIFICATION_PROFILE_DESTROYED,
                              content::Source<Profile>(profile_));

  // Register to inform new RenderViews that we're prerendering.
  notification_registrar_.Add(
      this, content::NOTIFICATION_WEB_CONTENTS_RENDER_VIEW_HOST_CREATED,
      content::Source<WebContents>(prerender_contents_.get()));

  // Register for redirect notifications sourced from |this|.
  notification_registrar_.Add(
      this, content::NOTIFICATION_RESOURCE_RECEIVED_REDIRECT,
      content::Source<WebContents>(prerender_contents_.get()));

  // Transfer over the user agent override.
  prerender_contents_.get()->SetUserAgentOverride(
      prerender_manager_->config().user_agent_override);

  content::NavigationController::LoadURLParams load_url_params(
      prerender_url_);
  load_url_params.referrer = referrer_;
  load_url_params.transition_type = (origin_ == ORIGIN_OMNIBOX ?
      content::PAGE_TRANSITION_TYPED : content::PAGE_TRANSITION_LINK);
  load_url_params.override_user_agent =
      prerender_manager_->config().is_overriding_user_agent ?
      content::NavigationController::UA_OVERRIDE_TRUE :
      content::NavigationController::UA_OVERRIDE_FALSE;
  prerender_contents_.get()->GetController().LoadURLWithParams(load_url_params);
}

bool PrerenderContents::GetChildId(int* child_id) const {
  CHECK(child_id);
  DCHECK_GE(child_id_, -1);
  *child_id = child_id_;
  return child_id_ != -1;
}

bool PrerenderContents::GetRouteId(int* route_id) const {
  CHECK(route_id);
  DCHECK_GE(route_id_, -1);
  *route_id = route_id_;
  return route_id_ != -1;
}

void PrerenderContents::SetFinalStatus(FinalStatus final_status) {
  DCHECK(final_status >= FINAL_STATUS_USED && final_status < FINAL_STATUS_MAX);
  DCHECK(final_status_ == FINAL_STATUS_MAX);

  final_status_ = final_status;
}

PrerenderContents::~PrerenderContents() {
  DCHECK_NE(FINAL_STATUS_MAX, final_status());
  DCHECK(
      prerendering_has_been_cancelled() || final_status() == FINAL_STATUS_USED);
  DCHECK_NE(ORIGIN_MAX, origin());

  prerender_manager_->RecordFinalStatusWithMatchCompleteStatus(
      origin(), experiment_id(), match_complete_status(), final_status());

  // Broadcast the removal of aliases.
  for (content::RenderProcessHost::iterator host_iterator =
           content::RenderProcessHost::AllHostsIterator();
       !host_iterator.IsAtEnd();
       host_iterator.Advance()) {
    content::RenderProcessHost* host = host_iterator.GetCurrentValue();
    host->Send(new PrerenderMsg_OnPrerenderRemoveAliases(alias_urls_));
  }

  // If we still have a WebContents, clean up anything we need to and then
  // destroy it.
  if (prerender_contents_.get())
    delete ReleasePrerenderContents();
}

void PrerenderContents::AddObserver(Observer* observer) {
  DCHECK_EQ(FINAL_STATUS_MAX, final_status_);
  observer_list_.AddObserver(observer);
}

void PrerenderContents::RemoveObserver(Observer* observer) {
  observer_list_.RemoveObserver(observer);
}

void PrerenderContents::Observe(int type,
                                const content::NotificationSource& source,
                                const content::NotificationDetails& details) {
  switch (type) {
    case chrome::NOTIFICATION_PROFILE_DESTROYED:
      Destroy(FINAL_STATUS_PROFILE_DESTROYED);
      return;

    case chrome::NOTIFICATION_APP_TERMINATING:
      Destroy(FINAL_STATUS_APP_TERMINATING);
      return;

    case content::NOTIFICATION_RESOURCE_RECEIVED_REDIRECT: {
      // RESOURCE_RECEIVED_REDIRECT can come for any resource on a page.
      // If it's a redirect on the top-level resource, the name needs
      // to be remembered for future matching, and if it redirects to
      // an https resource, it needs to be canceled. If a subresource
      // is redirected, nothing changes.
      DCHECK_EQ(content::Source<WebContents>(source).ptr(),
                prerender_contents_.get());
      ResourceRedirectDetails* resource_redirect_details =
          content::Details<ResourceRedirectDetails>(details).ptr();
      CHECK(resource_redirect_details);
      if (resource_redirect_details->resource_type ==
          ResourceType::MAIN_FRAME) {
        if (!AddAliasURL(resource_redirect_details->new_url))
          return;
      }
      break;
    }

    case content::NOTIFICATION_WEB_CONTENTS_RENDER_VIEW_HOST_CREATED: {
      if (prerender_contents_.get()) {
        DCHECK_EQ(content::Source<WebContents>(source).ptr(),
                  prerender_contents_.get());

        content::Details<RenderViewHost> new_render_view_host(details);
        OnRenderViewHostCreated(new_render_view_host.ptr());

        // When a new RenderView is created for a prerendering WebContents,
        // tell the new RenderView it's being used for prerendering before any
        // navigations occur.  Note that this is always triggered before the
        // first navigation, so there's no need to send the message just after
        // the WebContents is created.
        new_render_view_host->Send(
            new PrerenderMsg_SetIsPrerendering(
                new_render_view_host->GetRoutingID(),
                true));

        // Make sure the size of the RenderViewHost has been passed to the new
        // RenderView.  Otherwise, the size may not be sent until the
        // RenderViewReady event makes it from the render process to the UI
        // thread of the browser process.  When the RenderView receives its
        // size, is also sets itself to be visible, which would then break the
        // visibility API.
        new_render_view_host->WasResized();
        prerender_contents_->WasHidden();
      }
      break;
    }

    default:
      NOTREACHED() << "Unexpected notification sent.";
      break;
  }
}

void PrerenderContents::OnRenderViewHostCreated(
    RenderViewHost* new_render_view_host) {
}

size_t PrerenderContents::pending_prerender_count() const {
  return pending_prerenders_.size();
}

WebContents* PrerenderContents::CreateWebContents(
    SessionStorageNamespace* session_storage_namespace) {
  // TODO(ajwong): Remove the temporary map once prerendering is aware of
  // multiple session storage namespaces per tab.
  content::SessionStorageNamespaceMap session_storage_namespace_map;
  session_storage_namespace_map[std::string()] = session_storage_namespace;
  return WebContents::CreateWithSessionStorage(
      WebContents::CreateParams(profile_), session_storage_namespace_map);
}

void PrerenderContents::NotifyPrerenderStart() {
  DCHECK_EQ(FINAL_STATUS_MAX, final_status_);
  FOR_EACH_OBSERVER(Observer, observer_list_, OnPrerenderStart(this));
}

void PrerenderContents::NotifyPrerenderStopLoading() {
  FOR_EACH_OBSERVER(Observer, observer_list_, OnPrerenderStopLoading(this));
}

void PrerenderContents::NotifyPrerenderStop() {
  DCHECK_NE(FINAL_STATUS_MAX, final_status_);
  FOR_EACH_OBSERVER(Observer, observer_list_, OnPrerenderStop(this));
  observer_list_.Clear();
}

void PrerenderContents::NotifyPrerenderCreatedMatchCompleteReplacement(
    PrerenderContents* replacement) {
  FOR_EACH_OBSERVER(Observer, observer_list_,
                    OnPrerenderCreatedMatchCompleteReplacement(this,
                                                               replacement));
}

void PrerenderContents::DidUpdateFaviconURL(
    int32 page_id,
    const std::vector<content::FaviconURL>& urls) {
  VLOG(1) << "PrerenderContents::OnUpdateFaviconURL" << icon_url_;
  for (std::vector<content::FaviconURL>::const_iterator it = urls.begin();
       it != urls.end(); ++it) {
    if (it->icon_type == content::FaviconURL::FAVICON) {
      icon_url_ = it->icon_url;
      VLOG(1) << icon_url_;
      return;
    }
  }
}

bool PrerenderContents::AddAliasURL(const GURL& url) {
  const bool http = url.SchemeIs(chrome::kHttpScheme);
  const bool https = url.SchemeIs(chrome::kHttpsScheme);
  if (!http && !https) {
    DCHECK_NE(MATCH_COMPLETE_REPLACEMENT_PENDING, match_complete_status_);
    Destroy(FINAL_STATUS_UNSUPPORTED_SCHEME);
    return false;
  }
  if (https && !prerender_manager_->config().https_allowed) {
    DCHECK_NE(MATCH_COMPLETE_REPLACEMENT_PENDING, match_complete_status_);
    Destroy(FINAL_STATUS_HTTPS);
    return false;
  }
  if (match_complete_status_ != MATCH_COMPLETE_REPLACEMENT_PENDING &&
      prerender_manager_->HasRecentlyBeenNavigatedTo(origin(), url)) {
    Destroy(FINAL_STATUS_RECENTLY_VISITED);
    return false;
  }

  alias_urls_.push_back(url);

  for (content::RenderProcessHost::iterator host_iterator =
           content::RenderProcessHost::AllHostsIterator();
       !host_iterator.IsAtEnd();
       host_iterator.Advance()) {
    content::RenderProcessHost* host = host_iterator.GetCurrentValue();
    host->Send(new PrerenderMsg_OnPrerenderAddAlias(url));
  }

  return true;
}

bool PrerenderContents::Matches(
    const GURL& url,
    const SessionStorageNamespace* session_storage_namespace) const {
  if (session_storage_namespace &&
      session_storage_namespace_id_ != session_storage_namespace->id()) {
    return false;
  }
  return std::count_if(alias_urls_.begin(), alias_urls_.end(),
                       std::bind2nd(std::equal_to<GURL>(), url)) != 0;
}

void PrerenderContents::RenderProcessGone(base::TerminationStatus status) {
  Destroy(FINAL_STATUS_RENDERER_CRASHED);
}

void PrerenderContents::DidStopLoading(
    content::RenderViewHost* render_view_host) {
  has_stopped_loading_ = true;
  NotifyPrerenderStopLoading();
}

void PrerenderContents::DidStartProvisionalLoadForFrame(
    int64 frame_id,
    int64 parent_frame_id,
    bool is_main_frame,
    const GURL& validated_url,
    bool is_error_page,
    bool is_iframe_srcdoc,
    RenderViewHost* render_view_host) {
  if (is_main_frame) {
    if (!AddAliasURL(validated_url))
      return;

    // Usually, this event fires if the user clicks or enters a new URL.
    // Neither of these can happen in the case of an invisible prerender.
    // So the cause is: Some JavaScript caused a new URL to be loaded.  In that
    // case, the spinner would start again in the browser, so we must reset
    // has_stopped_loading_ so that the spinner won't be stopped.
    has_stopped_loading_ = false;
    has_finished_loading_ = false;
  }
}

void PrerenderContents::DidFinishLoad(int64 frame_id,
                                      const GURL& validated_url,
                                      bool is_main_frame,
                                      RenderViewHost* render_view_host) {
  if (is_main_frame)
    has_finished_loading_ = true;
}

void PrerenderContents::Destroy(FinalStatus final_status) {
  DCHECK_NE(final_status, FINAL_STATUS_USED);

  if (prerendering_has_been_cancelled_)
    return;

  if (child_id_ != -1 && route_id_ != -1) {
    // Cancel the prerender in the PrerenderTracker.  This is needed
    // because destroy may be called directly from the UI thread without calling
    // TryCancel().  This is difficult to completely avoid, since prerendering
    // can be cancelled before a RenderView is created.
    bool is_cancelled = prerender_manager()->prerender_tracker()->TryCancel(
        child_id_, route_id_, final_status);
    CHECK(is_cancelled);

    // A different final status may have been set already from another thread.
    // If so, use it instead.
    if (!prerender_manager()->prerender_tracker()->
            GetFinalStatus(child_id_, route_id_, &final_status)) {
      NOTREACHED();
    }
  }
  SetFinalStatus(final_status);

  prerendering_has_been_cancelled_ = true;
  prerender_manager_->AddToHistory(this);
  prerender_manager_->MoveEntryToPendingDelete(this, final_status);

  if (!prerender_manager_->IsControlGroup(experiment_id()) &&
      (prerendering_has_started() ||
       match_complete_status() == MATCH_COMPLETE_REPLACEMENT)) {
    NotifyPrerenderStop();
  }

  // We may destroy the PrerenderContents before we have initialized the
  // RenderViewHost. Otherwise set the Observer's PrerenderContents to NULL to
  // avoid any more messages being sent.
  if (render_view_host_observer_)
    render_view_host_observer_->set_prerender_contents(NULL);
}

base::ProcessMetrics* PrerenderContents::MaybeGetProcessMetrics() {
  if (process_metrics_.get() == NULL) {
    // If a PrenderContents hasn't started prerending, don't be fully formed.
    if (!GetRenderViewHost() || !GetRenderViewHost()->GetProcess())
      return NULL;
    base::ProcessHandle handle = GetRenderViewHost()->GetProcess()->GetHandle();
    if (handle == base::kNullProcessHandle)
      return NULL;
#if !defined(OS_MACOSX)
    process_metrics_.reset(base::ProcessMetrics::CreateProcessMetrics(handle));
#else
    process_metrics_.reset(base::ProcessMetrics::CreateProcessMetrics(
        handle,
        content::BrowserChildProcessHost::GetPortProvider()));
#endif
  }

  return process_metrics_.get();
}

void PrerenderContents::DestroyWhenUsingTooManyResources() {
  base::ProcessMetrics* metrics = MaybeGetProcessMetrics();
  if (metrics == NULL)
    return;

  size_t private_bytes, shared_bytes;
  if (metrics->GetMemoryBytes(&private_bytes, &shared_bytes) &&
      private_bytes > prerender_manager_->config().max_bytes) {
    Destroy(FINAL_STATUS_MEMORY_LIMIT_EXCEEDED);
  }
}

WebContents* PrerenderContents::ReleasePrerenderContents() {
  prerender_contents_->SetDelegate(NULL);
  render_view_host_observer_.reset();
  content::WebContentsObserver::Observe(NULL);
  return prerender_contents_.release();
}

RenderViewHost* PrerenderContents::GetRenderViewHostMutable() {
  return const_cast<RenderViewHost*>(GetRenderViewHost());
}

const RenderViewHost* PrerenderContents::GetRenderViewHost() const {
  if (!prerender_contents_.get())
    return NULL;
  return prerender_contents_->GetRenderViewHost();
}

void PrerenderContents::DidNavigate(
    const history::HistoryAddPageArgs& add_page_args) {
  add_page_vector_.push_back(add_page_args);
}

void PrerenderContents::CommitHistory(WebContents* tab) {
  HistoryTabHelper* history_tab_helper = HistoryTabHelper::FromWebContents(tab);
  for (size_t i = 0; i < add_page_vector_.size(); ++i)
    history_tab_helper->UpdateHistoryForNavigation(add_page_vector_[i]);
}

Value* PrerenderContents::GetAsValue() const {
  if (!prerender_contents_.get())
    return NULL;
  DictionaryValue* dict_value = new DictionaryValue();
  dict_value->SetString("url", prerender_url_.spec());
  base::TimeTicks current_time = base::TimeTicks::Now();
  base::TimeDelta duration = current_time - load_start_time_;
  dict_value->SetInteger("duration", duration.InSeconds());
  dict_value->SetBoolean("is_loaded", prerender_contents_ &&
                                      !prerender_contents_->IsLoading());
  return dict_value;
}

bool PrerenderContents::IsCrossSiteNavigationPending() const {
  if (!prerender_contents_)
    return false;
  return (prerender_contents_->GetSiteInstance() !=
          prerender_contents_->GetPendingSiteInstance());
}


}  // namespace prerender