Avoid generating thumbnails while WebContents is destructed.

chrome/browser/ui/tab_contents/tab_contents.cc

Index: chrome/browser/ui/tab_contents/tab_contents.cc
diff --git a/chrome/browser/ui/tab_contents/tab_contents.cc b/chrome/browser/ui/tab_contents/tab_contents.cc
index 139648429ba4096c4f1db1027accbc9b0b58ba57..59c83e1b0430e430bcc4b7e88551242e08ca9c66 100644
--- a/chrome/browser/ui/tab_contents/tab_contents.cc
+++ b/chrome/browser/ui/tab_contents/tab_contents.cc
@@ -207,16 +207,6 @@ TabContents::TabContents(WebContents* contents)
 TabContents::~TabContents() {
   in_destructor_ = true;
 
-  // Need to reset |thumbnail_generator_| here before |web_contents_| is
-  // deleted because destructing |web_contents_| can end up causing the
-  // thumbnailer to generate a thumbnail. Since TabContents can be
-  // destructed during shutdown, trying to generate a thumbnail by sending an
-  // IPC message to the GPU process is not safe. Sending
-  // chrome::NOTIFICATION_TAB_CONTENTS_DESTROYED can also cause the thumbnailer

[mazda, 2012/08/30 17:19:18]

I was forgetting that we need to deal with this case. We want to avoid
generating thumbnails here, too. WebContents::IsBeingDestroyed cannot be used
for this case because it's before entering its dtor.
I wrote an idea to deal with this case in another comment.

[Avi (use Gerrit), 2012/08/30 18:16:26]

Note that NOTIFICATION_TAB_CONTENTS_DESTROYED is going away when I kill
TabContents.

[mazda, 2012/08/30 19:39:22]

That's a great. Then WebContents::IsBeingDestroyed can be used.

-  // to generate a thumbnail, so this must be placed before sending the
-  // notification.
-  thumbnail_generator_.reset();
-
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_TAB_CONTENTS_DESTROYED,
       content::Source<TabContents>(this),