Avoid generating thumbnails while WebContents is destructed.

content/public/browser/web_contents.h

 // 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.
 
 #ifndef CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_H_
 #define CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_H_
 
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "base/process_util.h"
@@ skipping 165 matching lines @@
   // Return the character encoding of the page.
   virtual const std::string& GetEncoding() const = 0;
 
   // True if this is a secure page which displayed insecure content.
   virtual bool DisplayedInsecureContent() const = 0;
 
   // Internal state ------------------------------------------------------------
 
   // This flag indicates whether the WebContents is currently being
   // screenshotted.
-  virtual void SetCapturingContents(bool cap)  = 0;
+  virtual void SetCapturingContents(bool cap) = 0;
 
   // Indicates whether this tab should be considered crashed. The setter will
   // also notify the delegate when the flag is changed.
   virtual bool IsCrashed() const  = 0;
   virtual void SetIsCrashed(base::TerminationStatus status, int error_code) = 0;
 
-  virtual base::TerminationStatus GetCrashedStatus() const  = 0;
+  virtual base::TerminationStatus GetCrashedStatus() const = 0;
 
   // Whether the tab is in the process of being destroyed.
-  // Added as a tentative work-around for focus related bug #4633.  This allows
-  // us not to store focus when a tab is being closed.
-  virtual bool IsBeingDestroyed() const  = 0;
+  virtual bool IsBeingDestroyed() const = 0;
 
   // Convenience method for notifying the delegate of a navigation state
   // change. See InvalidateType enum.
   virtual void NotifyNavigationStateChanged(unsigned changed_flags) = 0;
 
   // Get the last time that the WebContents was made visible with WasShown()
   virtual base::TimeTicks GetLastSelectedTime() const = 0;
 
   // Invoked when the WebContents becomes shown/hidden.
   virtual void WasShown() = 0;
@@ skipping 180 matching lines @@
   // Focuses the location bar.
   virtual void SetFocusToLocationBar(bool select_all) = 0;
 
   // Does this have an opener associated with it?
   virtual bool HasOpener() const = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_H_