move favicon download code from chrome/ into content/

chrome/browser/prerender/prerender_render_view_host_observer.h

Index: chrome/browser/prerender/prerender_render_view_host_observer.h
diff --git a/chrome/browser/prerender/prerender_render_view_host_observer.h b/chrome/browser/prerender/prerender_render_view_host_observer.h
index e6ecf8e25aba292b5e3ba6029097cbdc1986fc67..709489c73af8eb3eb3b484f4ea5f78ccb3def172 100644
--- a/chrome/browser/prerender/prerender_render_view_host_observer.h
+++ b/chrome/browser/prerender/prerender_render_view_host_observer.h
@@ -9,9 +9,9 @@
 
 #include "content/public/browser/render_view_host_observer.h"
 
-struct FaviconURL;
 
 namespace content {
+struct FaviconURL;
 class RenderViewHost;
 }
 
@@ -40,7 +40,7 @@ class PrerenderRenderViewHostObserver : public content::RenderViewHostObserver {
 
  private:
   // Message handlers.
-  void OnUpdateFaviconURL(int32 page_id, const std::vector<FaviconURL>& urls);
+
   void OnMaybeCancelPrerenderForHTML5Media();
   void OnCancelPrerenderForPrinting();