Fix crash when using Instant.

chrome/browser/ui/cocoa/tab_contents/previewable_contents_controller.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 CHROME_BROWSER_UI_COCOA_TAB_CONTENTS_PREVIEWABLE_CONTENTS_CONTROLLER_H_
 #define CHROME_BROWSER_UI_COCOA_TAB_CONTENTS_PREVIEWABLE_CONTENTS_CONTROLLER_H_
 
 #import <Cocoa/Cocoa.h>
 
 namespace content {
@@ skipping 22 matching lines @@
 
 @property(readonly, nonatomic) NSView* activeContainer;
 
 // Sets the current preview and installs its WebContentsView into the view
 // hierarchy.  Hides the active view.  |preview| must not be NULL.
 - (void)showPreview:(content::WebContents*)preview;
 
 // Closes the current preview and shows the active view.
 - (void)hidePreview;
 
+// Called when a new tab with |contents| is added, so that we can check to see
+// if it's the preview being committed (and adjust internal state accordingly).
+- (void)onInsertTabWithContents:(content::WebContents*)contents;
+
 // Returns YES if the preview contents is currently showing.
 - (BOOL)isShowingPreview;
 
 @end
 
 #endif  // CHROME_BROWSER_UI_COCOA_TAB_CONTENTS_PREVIEWABLE_CONTENTS_CONTROLLER_H_