Speculative fix for instant overlay crash

chrome/browser/ui/cocoa/tab_contents/instant_overlay_controller_mac.mm

 // Copyright 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.
 
 #include "chrome/browser/ui/cocoa/tab_contents/instant_overlay_controller_mac.h"
 
 #include "chrome/browser/search/search.h"
 #include "chrome/browser/ui/browser.h"
 #import "chrome/browser/ui/cocoa/browser_window_controller.h"
 #include "chrome/browser/ui/cocoa/tab_contents/instant_overlay_controller_mac.h"
 #import "chrome/browser/ui/cocoa/tab_contents/overlayable_contents_controller.h"
 #include "chrome/browser/ui/search/instant_overlay_model.h"
 #include "chrome/browser/ui/search/search_model.h"
 #include "chrome/browser/ui/search/search_tab_helper.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "content/public/browser/notification_source.h"
+#include "content/public/browser/notification_types.h"
 
 InstantOverlayControllerMac::InstantOverlayControllerMac(
     Browser* browser,
     BrowserWindowController* window,
     OverlayableContentsController* overlay)
     : InstantOverlayController(browser),
       window_(window),
       overlay_(overlay) {
 }
 
@@ skipping 36 matching lines @@
           SearchTabHelper::FromWebContents(active_web_contents);
       if (search_tab_helper &&
           search_tab_helper->model()->mode().is_origin_default()) {
         search_tab_helper->model()->SetTopBarsVisible(
             ![overlay_ isShowingOverlay]);
       }
     }
   }
 
   [window_ updateBookmarkBarStateForInstantOverlay];
+
+  registrar_.RemoveAll();
+  if (model.GetOverlayContents()) {
+    registrar_.Add(
+        this,
+        content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
+        content::Source<content::WebContents>(model.GetOverlayContents()));
+  }
 }
+
+void InstantOverlayControllerMac::Observe(
+    int type,
+    const content::NotificationSource& source,
+    const content::NotificationDetails& details) {
+  [overlay_ onWebContentsDestroyed:
+          content::Source<content::WebContents>(source).ptr()];
+}