Gracefully handle tab update events for closing tabs.

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

Index: chrome/browser/extensions/api/tabs/tabs_event_router.cc
diff --git a/chrome/browser/extensions/api/tabs/tabs_event_router.cc b/chrome/browser/extensions/api/tabs/tabs_event_router.cc
index bcee3c6410ed5131037cfb9b702378db980ba8e8..6f5d5207b3a717a48fc2ac4b6d0551bd44d27064 100644
--- a/chrome/browser/extensions/api/tabs/tabs_event_router.cc
+++ b/chrome/browser/extensions/api/tabs/tabs_event_router.cc
@@ -396,7 +396,8 @@ 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));