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 480 matching lines @@
     }
   }
 
   SkBitmap clipped_bitmap;
   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();
   // Skip if we don't need to update the thumbnail.
-  if (!ShouldUpdateThumbnail(profile, top_sites, url))
+  if (!ShouldUpdateThumbnail(web_contents))
     return;
 
   AsyncUpdateThumbnail(web_contents);
 }
 
 void ThumbnailGenerator::UpdateThumbnail(
     WebContents* web_contents, const SkBitmap& thumbnail,
     const ThumbnailGenerator::ClipResult& clip_result) {
 
   Profile* profile =
@@ skipping 57 matching lines @@
       skia::GetTopDevice(*temp_canvas)->accessBitmap(false);
   ClipResult clip_result;
   SkBitmap thumbnail = CreateThumbnail(bmp_with_scrollbars,
                                        kThumbnailWidth,
                                        kThumbnailHeight,
                                        ThumbnailGenerator::kClippedThumbnail,
                                        &clip_result);
   UpdateThumbnail(web_contents.get(), thumbnail, clip_result);
 }
 
-bool ThumbnailGenerator::ShouldUpdateThumbnail(Profile* profile,
-                                               history::TopSites* top_sites,
-                                               const GURL& url) {
+bool ThumbnailGenerator::ShouldUpdateThumbnail(
+    content::WebContents* web_contents) {
+  const GURL& url = web_contents->GetURL();
+  Profile* profile =
+      Profile::FromBrowserContext(web_contents->GetBrowserContext());

[mazda, 2012/05/03 19:57:31]

NULL check for profile is needed.

+  history::TopSites* top_sites = profile->GetTopSites();

[mazda, 2012/05/03 19:57:31]

Could you move this just before |top_sites| is used and add NULL check for it.

+  content::RenderWidgetHostView* rwhv = web_contents->GetRenderWidgetHostView();
+  if (!rwhv->HasSurface())

[mazda, 2012/05/03 19:57:31]

In order to use this function here, it needs to handle the following cases.
1. Backing store is available.
2. Accelerated surface is available.

I added comments to HasSurface, but I have not tested them.

+    return false;
   if (!profile || !top_sites)

[mazda, 2012/05/03 19:57:31]

Please delete this with the changes above.

     return false;
   // Skip if it's in the incognito mode.
   if (profile->IsOffTheRecord())
     return false;
   // Skip if the given URL is not appropriate for history.
   if (!HistoryService::CanAddURL(url))
     return false;
   // Skip if the top sites list is full, and the URL is not known.
   if (top_sites->IsFull() && !top_sites->IsKnownURL(url))
     return false;
@@ skipping 14 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;
 }