Fix Native Messaging to handle missing caller RenderWidgetHost.

chrome/browser/extensions/api/messaging/message_service.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/extensions/api/messaging/message_service.h"
 
 #include "base/atomic_sequence_num.h"
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/json/json_writer.h"
@@ skipping 385 matching lines @@
   if (policy_permission == DISALLOW) {
     DispatchOnDisconnect(source, receiver_port_id, kProhibitedByPoliciesError);
     return;
   }
 
   scoped_ptr<MessageChannel> channel(new MessageChannel());
   channel->opener.reset(new ExtensionMessagePort(source, MSG_ROUTING_CONTROL,
                                                  source_extension_id));
 
   // Get handle of the native view and pass it to the native messaging host.
+  content::RenderWidgetHost* render_widget_host =
+      content::RenderWidgetHost::FromID(source_process_id, source_routing_id);
   gfx::NativeView native_view =
-      content::RenderWidgetHost::FromID(source_process_id, source_routing_id)->
-          GetView()->GetNativeView();
+      render_widget_host ? render_widget_host->GetView()->GetNativeView()
+                         : NULL;

[not at google - send to devlin, 2014/12/11 17:24:42]

Are we supposed to use nullptr these days? I'm losing track.

Anyway, I may be missing something here, but I traced through the call stack and
I can't see the native view actually used anywhere.

Under the assumption I *am* missing something, then this change lgtm, though it
seems weird passing a potentially NULL native view. You could document in
NativeMessageHost::Create that the view can be null. Or even better... delete it
entirely :)

[Sergey Ulanov, 2014/12/11 19:25:29]

Yes, it should be nullptr. This is my first change in more than 2 month
(parental leave), so I forgot about it. Thanks for catching it.
It's used only on windows to pass chrome window handle to the native process,
e.g. so that it can set correct parent for UAC prompts. See
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/ext...
Added a comment in native_process_launcer.h

[not at google - send to devlin, 2014/12/11 20:19:46]

Where is native_view used then?

 
   std::string error = kReceivingEndDoesntExistError;
   scoped_ptr<NativeMessageHost> native_host = NativeMessageHost::Create(
       native_view,
       source_extension_id,
       native_app_name,
       policy_permission == ALLOW_ALL,
       &error);
 
   // Abandon the channel.
@@ skipping 447 matching lines @@
                                              int channel_id) {
   MessageChannelMap::iterator channel_iter = channels_.find(channel_id);
   if (channel_iter != channels_.end()) {
     for (const PendingMessage& message : queue) {
       DispatchMessage(message.first, channel_iter->second, message.second);
     }
   }
 }
 
 }  // namespace extensions