drive: Fix a DCHECK failure at shutdown after Drive is disabled

chrome/browser/chromeos/extensions/file_browser_event_router.cc

 // 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.
 
 #include "chrome/browser/chromeos/extensions/file_browser_event_router.h"
 
 #include "base/bind.h"
 #include "base/json/json_writer.h"
 #include "base/message_loop.h"
 #include "base/prefs/public/pref_change_registrar.h"
@@ skipping 540 matching lines @@
 
   profile_->GetExtensionEventRouter()->DispatchEventToRenderers(
       extensions::event_names::kOnFileBrowserDiskChanged, args.Pass(), NULL,
       GURL());
 }
 
 void FileBrowserEventRouter::DispatchMountCompletedEvent(
     DiskMountManager::MountEvent event,
     chromeos::MountError error_code,
     const DiskMountManager::MountPointInfo& mount_info) {
-  if (!profile_ || mount_info.mount_type == chromeos::MOUNT_TYPE_INVALID) {
+  // profile_ is NULL if ShutdownOnUIThread() is called earlier. This can
+  // happen at shutdown.
+  if (!profile_)
+    return;
+
+  if (mount_info.mount_type == chromeos::MOUNT_TYPE_INVALID) {
     NOTREACHED();
     return;
   }
 
   scoped_ptr<ListValue> args(new ListValue());
   DictionaryValue* mount_info_value = new DictionaryValue();
   args->Append(mount_info_value);
   mount_info_value->SetString("eventType",
       event == DiskMountManager::MOUNTING ? "mount" : "unmount");
   mount_info_value->SetString("status", MountErrorToString(error_code));
@@ skipping 303 matching lines @@
   return scoped_refptr<RefcountedProfileKeyedService>(
       new FileBrowserEventRouter(profile));
 }
 
 bool FileBrowserEventRouterFactory::ServiceHasOwnInstanceInIncognito() const {
   // Explicitly and always allow this router in guest login mode.   see
   // chrome/browser/profiles/profile_keyed_base_factory.h comment
   // for the details.
   return true;
 }