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..d16924e379f1d11f769cbb2e37be1fede3edfc32 100644
--- a/chrome/browser/tab_contents/thumbnail_generator.cc
+++ b/chrome/browser/tab_contents/thumbnail_generator.cc
@@ -502,8 +502,10 @@ void ThumbnailGenerator::UpdateThumbnailIfNecessary(
   Profile* profile =
       Profile::FromBrowserContext(web_contents->GetBrowserContext());
   history::TopSites* top_sites = profile->GetTopSites();
+  bool surface_available =
+      web_contents->GetRenderWidgetHostView()->IsSurfaceAvailableForCopy();
   // Skip if we don't need to update the thumbnail.
-  if (!ShouldUpdateThumbnail(profile, top_sites, url))
+  if (!ShouldUpdateThumbnail(profile, top_sites, url, surface_available))

[mazda, 2012/05/04 22:20:32]

How about just doing as follows?

if (!surface_available || !ShouldUpdateThumbnail(profile, top_sites, url))

[mmocny, 2012/05/07 13:28:23]

Yes, it is certainly a bit silly to move the bool around just to test.

I wasn't sure if the ShouldUpdateThumbnail could ever be used in other
locations, and so moving it into there would make the condition explicit.

But, I can move it out.

On 2012/05/04 22:20:32, mazda wrote:

[mazda, 2012/05/07 16:37:19]

We do not plan to use ShouldUpdateThumbnail in other location for now, so I
think it's OK to move it out.

     return;
 
   AsyncUpdateThumbnail(web_contents);
@@ -583,7 +585,10 @@ void ThumbnailGenerator::AsyncUpdateThumbnailFinish(
 
 bool ThumbnailGenerator::ShouldUpdateThumbnail(Profile* profile,
                                                history::TopSites* top_sites,
-                                               const GURL& url) {
+                                               const GURL& url,
+                                               bool surface_available) {
+  if (!surface_available)
+    return false;
   if (!profile || !top_sites)
     return false;
   // Skip if it's in the incognito mode.