chrome/renderer/prerender/prerender_helper.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome/renderer/prerender/prerender_helper.h"
   6
   7 #include "base/metrics/field_trial.h"
   8 #include "base/metrics/histogram.h"
   9 #include "chrome/common/prerender_messages.h"
  10 #include "content/public/renderer/document_state.h"
  11 #include "content/public/renderer/render_view.h"
  12 #include "third_party/WebKit/public/web/WebFrame.h"
  13 #include "third_party/WebKit/public/web/WebView.h"
  14
  15 using content::DocumentState;
  16
  17 namespace {
  18
  19 // Updates the visibility state of the RenderView.  Must be called whenever
  20 // prerendering starts or finishes and the page is about to be show.  At both
  21 // those times, the RenderView is hidden.
  22 void UpdateVisibilityState(content::RenderView* render_view) {
  23   if (render_view->GetWebView()) {
  24     render_view->GetWebView()->setVisibilityState(
  25         render_view->GetVisibilityState(), false);
  26   }
  27 }
  28
  29 }  // namespace
  30
  31 namespace prerender {
  32
  33 PrerenderHelper::PrerenderHelper(content::RenderView* render_view)
  34     : content::RenderViewObserver(render_view),
  35       content::RenderViewObserverTracker<PrerenderHelper>(render_view) {
  36   UpdateVisibilityState(render_view);
  37 }
  38
  39 PrerenderHelper::~PrerenderHelper() {
  40 }
  41
  42 // static.
  43 bool PrerenderHelper::IsPrerendering(const content::RenderView* render_view) {
  44   return PrerenderHelper::Get(render_view) != NULL;
  45 }
  46
  47 bool PrerenderHelper::OnMessageReceived(
  48     const IPC::Message& message) {
  49   IPC_BEGIN_MESSAGE_MAP(PrerenderHelper, message)
  50     IPC_MESSAGE_HANDLER(PrerenderMsg_SetIsPrerendering, OnSetIsPrerendering)
  51   IPC_END_MESSAGE_MAP()
  52   // Return false on ViewMsg_SetIsPrerendering so other observers can see the
  53   // message.
  54   return false;
  55 }
  56
  57 void PrerenderHelper::OnSetIsPrerendering(bool is_prerendering) {
  58   // Immediately after construction, |this| may receive the message that
  59   // triggered its creation.  If so, ignore it.
  60   if (is_prerendering)
  61     return;
  62
  63   content::RenderView* view = render_view();
  64   // |this| must be deleted so PrerenderHelper::IsPrerendering returns false
  65   // when the visibility state is updated, so the visibility state string will
  66   // not be "prerendered".
  67   delete this;
  68
  69   UpdateVisibilityState(view);
  70 }
  71
  72 }  // namespace prerender