Enable resource prefetch from the browser process.

chrome/renderer/chrome_content_renderer_client.cc

Index: chrome/renderer/chrome_content_renderer_client.cc
diff --git a/chrome/renderer/chrome_content_renderer_client.cc b/chrome/renderer/chrome_content_renderer_client.cc
index dbd497294c2d42bbc8de32dbd567792bdbbdd9c6..f3e2313a696a00493874c8ab7fc1bfde197fc016 100644
--- a/chrome/renderer/chrome_content_renderer_client.cc
+++ b/chrome/renderer/chrome_content_renderer_client.cc
@@ -51,6 +51,7 @@
 #include "chrome/renderer/playback_extension.h"
 #include "chrome/renderer/plugins/chrome_plugin_placeholder.h"
 #include "chrome/renderer/plugins/plugin_uma.h"
+#include "chrome/renderer/prefetch_helper.h"
 #include "chrome/renderer/prerender/prerender_dispatcher.h"
 #include "chrome/renderer/prerender/prerender_helper.h"
 #include "chrome/renderer/prerender/prerender_media_load_deferrer.h"
@@ -423,7 +424,9 @@ void ChromeContentRendererClient::RenderFrameCreated(
   if (render_frame->GetRenderView()->GetMainRenderFrame() == render_frame) {
     // Only attach NetErrorHelper to the main frame, since only the main frame
     // should get error pages.
+    // PrefetchHelper is also needed only for main frames.
     new NetErrorHelper(render_frame);
+    new prefetch::PrefetchHelper(render_frame);
   }
 }