Fix top crash due to r110394 - TabContentsViewCocoa renderWidgetHostWasResized

chrome/browser/tab_contents/tab_contents_view_mac.mm

 // Copyright (c) 2011 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.
 
 #import <Carbon/Carbon.h>
 
 #include "chrome/browser/tab_contents/tab_contents_view_mac.h"
 
 #include <string>
 
@@ skipping 501 matching lines @@
 
 - (void)setFrameWithDeferredUpdate:(NSRect)frameRect {
   [super setFrame:frameRect];
   [self performSelector:@selector(renderWidgetHostWasResized)
              withObject:nil
              afterDelay:0];
 }
 
 - (void)renderWidgetHostWasResized {
   TabContents* tabContents = [self tabContents];
-  if (tabContents->render_view_host())
+  if (tabContents && tabContents->render_view_host())
     tabContents->render_view_host()->WasResized();
 }
 
 // NSDraggingSource methods
 
 // Returns what kind of drag operations are available. This is a required
 // method for NSDraggingSource.
 - (NSDragOperation)draggingSourceOperationMaskForLocal:(BOOL)isLocal {
   if (dragSource_.get())
     return [dragSource_ draggingSourceOperationMaskForLocal:isLocal];
@@ skipping 73 matching lines @@
       [[[notification userInfo] objectForKey:kSelectionDirection]
         unsignedIntegerValue];
   if (direction == NSDirectSelection)
     return;
 
   [self tabContents]->
       FocusThroughTabTraversal(direction == NSSelectingPrevious);
 }
 
 @end