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_frame.h"
  12 #include "content/public/renderer/render_view.h"
  13 #include "third_party/WebKit/public/web/WebFrame.h"
  14 #include "third_party/WebKit/public/web/WebView.h"
  15
  16 using content::DocumentState;
  17
  18 namespace {
  19
  20 // Updates the visibility state of the RenderFrame.  Must be called whenever
  21 // prerendering starts or finishes and the page is about to be show.  At both
  22 // those times, the RenderFrame is hidden.
  23 void UpdateVisibilityState(content::RenderFrame* render_frame) {
  24   // TODO(jam): until the prerendering code works on frames instead of views, we
  25   // have to do this awkward check.
  26   content::RenderView* render_view = render_frame->GetRenderView();
  27   if (render_view->GetMainRenderFrame() == render_frame) {
  28     render_view->GetWebView()->setVisibilityState(
  29         render_view->GetVisibilityState(), false);
  30   }
  31 }
  32
  33 }  // namespace
  34
  35 namespace prerender {
  36
  37 PrerenderHelper::PrerenderHelper(content::RenderFrame* render_frame)
  38     : content::RenderFrameObserver(render_frame),
  39       content::RenderFrameObserverTracker<PrerenderHelper>(render_frame) {
  40   UpdateVisibilityState(render_frame);
  41 }
  42
  43 PrerenderHelper::~PrerenderHelper() {
  44 }
  45
  46 // static.
  47 bool PrerenderHelper::IsPrerendering(const content::RenderFrame* render_frame) {
  48   return PrerenderHelper::Get(render_frame) != NULL;
  49 }
  50
  51 bool PrerenderHelper::OnMessageReceived(
  52     const IPC::Message& message) {
  53   IPC_BEGIN_MESSAGE_MAP(PrerenderHelper, message)
  54     IPC_MESSAGE_HANDLER(PrerenderMsg_SetIsPrerendering, OnSetIsPrerendering)
  55   IPC_END_MESSAGE_MAP()
  56   // Return false on ViewMsg_SetIsPrerendering so other observers can see the
  57   // message.
  58   return false;
  59 }
  60
  61 void PrerenderHelper::OnSetIsPrerendering(bool is_prerendering) {
  62   // Immediately after construction, |this| may receive the message that
  63   // triggered its creation.  If so, ignore it.
  64   if (is_prerendering)
  65     return;
  66
  67   content::RenderFrame* frame = render_frame();
  68   // |this| must be deleted so PrerenderHelper::IsPrerendering returns false
  69   // when the visibility state is updated, so the visibility state string will
  70   // not be "prerendered".
  71   delete this;
  72
  73   UpdateVisibilityState(frame);
  74 }
  75
  76 }  // namespace prerender