Avoid any race conditions with RenderFrame getting notified that it's prerendering.

chrome/renderer/chrome_content_renderer_client.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/renderer/chrome_content_renderer_client.h"
 
 #include "base/command_line.h"
 #include "base/debug/crash_logging.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
@@ skipping 347 matching lines @@
   if (chrome_observer_.get()) {
     content_settings->SetContentSettingRules(
         chrome_observer_->content_setting_rules());
   }
 
   new extensions::ExtensionFrameHelper(render_frame);
 
 #if defined(ENABLE_PLUGINS)
   new PepperHelper(render_frame);
 #endif
+
+  // TODO(jam): when a RenderFrame is per WebFrame, this can be simplified by
+  // getting a RenderFrame's WebFrame and calling its parent() method.
+  if (render_frame->GetRenderView()->GetMainRenderFrame() != render_frame) {
+    // Avoid any race conditions from having the browser tell subframes that
+    // they're prerendering.
+    if (prerender::PrerenderHelper::IsPrerendering(
+            render_frame->GetRenderView()->GetMainRenderFrame())) {
+      new prerender::PrerenderHelper(render_frame);
+    }
+  }
 }
 
 void ChromeContentRendererClient::RenderViewCreated(
     content::RenderView* render_view) {
   new extensions::ExtensionHelper(render_view, extension_dispatcher_.get());
   new PageLoadHistograms(render_view);
 #if defined(ENABLE_PRINTING)
   new printing::PrintWebViewHelper(render_view);
 #endif
 #if defined(ENABLE_SPELLCHECK)
@@ skipping 995 matching lines @@
   CommandLine* command_line = CommandLine::ForCurrentProcess();
   return !command_line->HasSwitch(switches::kExtensionProcess);
 }
 
 blink::WebWorkerPermissionClientProxy*
 ChromeContentRendererClient::CreateWorkerPermissionClientProxy(
     content::RenderFrame* render_frame,
     blink::WebFrame* frame) {
   return new WorkerPermissionClientProxy(render_frame, frame);
 }