Do not attempt to download favicons with 404 status in WebView

android_webview/browser/icon_helper.h

 // Copyright (c) 2013 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.
 
 #ifndef ANDROID_WEBVIEW_BROWSER_ICON_HELPER_H_
 #define ANDROID_WEBVIEW_BROWSER_ICON_HELPER_H_
 
 #include <string>
+#include "base/containers/hash_tables.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "url/gurl.h"
 
 class SkBitmap;
 
 namespace content {
 struct FaviconURL;
 }
 
 namespace gfx {
@@ skipping 17 matching lines @@
   };
 
   explicit IconHelper(content::WebContents* web_contents);
   virtual ~IconHelper();
 
   void SetListener(Listener* listener);
 
   // From WebContentsObserver
   virtual void DidUpdateFaviconURL(int32 page_id,
       const std::vector<content::FaviconURL>& candidates) OVERRIDE;
+  virtual void DidStartNavigationToPendingEntry(
+      const GURL& url,
+      content::NavigationController::ReloadType reload_type) OVERRIDE;
 
   void DownloadFaviconCallback(
       int id,
       int http_status_code,
       const GURL& image_url,
       const std::vector<SkBitmap>& bitmaps,
       const std::vector<gfx::Size>& original_bitmap_sizes);
 
  private:
+  void MarkUnableToDownloadFavicon(const GURL& icon_url);
+  bool WasUnableToDownloadFavicon(const GURL& icon_url) const;
+  void ClearUnableToDownloadFavicons();
+
   Listener* listener_;
 
+  typedef uint32 MissingFaviconURLHash;
+  base::hash_set<MissingFaviconURLHash> missing_favicon_urls_;
+
   DISALLOW_COPY_AND_ASSIGN(IconHelper);
 };
 
 }  // namespace android_webview
 
 #endif  // ANDROID_WEBVIEW_BROWSER_ICON_HELPER_H_