Gracefully handle tab update events for closing tabs.

chrome/browser/extensions/api/tabs/tabs_event_router.cc

 // Copyright 2013 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/extensions/api/tabs/tabs_event_router.h"
 
 #include "base/json/json_writer.h"
 #include "base/values.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/api/tabs/tabs_constants.h"
@@ skipping 378 matching lines @@
   DispatchEvent(profile,
                 tabs::OnMoved::kEventName,
                 args.Pass(),
                 EventRouter::USER_GESTURE_UNKNOWN);
 }
 
 void TabsEventRouter::TabUpdated(WebContents* contents, bool did_navigate) {
   TabEntry* entry = GetTabEntry(contents);
   scoped_ptr<base::DictionaryValue> changed_properties;
 
-  CHECK(entry);
+  if (!entry)
+    return;
 
   if (did_navigate)
     changed_properties.reset(entry->DidNavigate(contents));
   else
     changed_properties.reset(entry->UpdateLoadState(contents));
 
   if (changed_properties)
     DispatchTabUpdatedEvent(contents, changed_properties.Pass());
 }
 
@@ skipping 179 matching lines @@
 void TabsEventRouter::OnFaviconUpdated(favicon::FaviconDriver* favicon_driver,
                                        bool icon_url_changed) {
   if (icon_url_changed) {
     favicon::ContentFaviconDriver* content_favicon_driver =
         static_cast<favicon::ContentFaviconDriver*>(favicon_driver);
     FaviconUrlUpdated(content_favicon_driver->web_contents());
   }
 }
 
 }  // namespace extensions