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      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
     77