Prevent browser thumbnailer from trying to read from frontbuffer (surface texture) when none exists.

chrome/browser/tab_contents/thumbnail_generator.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/browser/tab_contents/thumbnail_generator.h"
 
 #include <algorithm>
 #include <map>
 
 #include "base/bind.h"
@@ skipping 425 matching lines @@
   bitmap.extractSubset(&clipped_bitmap, src_rect);
   return clipped_bitmap;
 }
 
 void ThumbnailGenerator::UpdateThumbnailIfNecessary(
     WebContents* web_contents) {
   const GURL& url = web_contents->GetURL();
   Profile* profile =
       Profile::FromBrowserContext(web_contents->GetBrowserContext());
   history::TopSites* top_sites = profile->GetTopSites();
+  bool surface_available =
+      web_contents->GetRenderWidgetHostView()->IsSurfaceAvailableForCopy();
+  // Skip if we can't update the thumbnail.
+  if (!surface_available)
+    return;
   // Skip if we don't need to update the thumbnail.
   if (!ShouldUpdateThumbnail(profile, top_sites, url))
     return;
 
   AsyncUpdateThumbnail(web_contents);
 }
 
 void ThumbnailGenerator::UpdateThumbnail(
     WebContents* web_contents, const SkBitmap& thumbnail,
     const ThumbnailGenerator::ClipResult& clip_result) {
@@ skipping 97 matching lines @@
 
 void ThumbnailGenerator::DidStartLoading() {
   load_interrupted_ = false;
 }
 
 void ThumbnailGenerator::StopNavigation() {
   // This function gets called when the page loading is interrupted by the
   // stop button.
   load_interrupted_ = true;
 }