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

chrome/browser/tab_contents/thumbnail_generator.cc

Index: chrome/browser/tab_contents/thumbnail_generator.cc
diff --git a/chrome/browser/tab_contents/thumbnail_generator.cc b/chrome/browser/tab_contents/thumbnail_generator.cc
index 162094b85936b01bd7cd204243670ba5e27907e1..426128cf3b98a4bac6442f08ad89fe161340e860 100644
--- a/chrome/browser/tab_contents/thumbnail_generator.cc
+++ b/chrome/browser/tab_contents/thumbnail_generator.cc
@@ -498,12 +498,8 @@ SkBitmap ThumbnailGenerator::GetClippedBitmap(const SkBitmap& 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);
@@ -581,9 +577,15 @@ void ThumbnailGenerator::AsyncUpdateThumbnailFinish(
   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.