Fix a race where backgroud page might ack an event before we're ready

extensions/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 "extensions/browser/event_router.h"
 
 #include <utility>
 
 #include "base/atomic_sequence_num.h"
 #include "base/bind.h"
@@ skipping 137 matching lines @@
 // static
 void EventRouter::DispatchEvent(IPC::Sender* ipc_sender,
                                 void* browser_context_id,
                                 const std::string& extension_id,
                                 const std::string& event_name,
                                 scoped_ptr<ListValue> event_args,
                                 UserGestureState user_gesture,
                                 const EventFilteringInfo& info) {
   int event_id = g_extension_event_id.GetNext();
 
+  if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
+    BrowserThread::PostTask(

[not at google - send to devlin, 2015/05/15 21:55:29]

comment when this is the case, what happens in that case, what the problem is,
and what you're planning on doing about it (maybe just a bug link).

[lazyboy, 2015/05/16 00:07:43]

Done.

+        BrowserThread::UI, FROM_HERE,
+        base::Bind(&EventRouter::IncrementInFlightEventsOnUI,
+                   browser_context_id, extension_id, event_id, event_name));
+  } else {
+    IncrementInFlightEventsOnUI(browser_context_id, extension_id, event_id,
+                                event_name);
+  }
+
   DispatchExtensionMessage(ipc_sender, browser_context_id, extension_id,
                            event_id, event_name, event_args.get(), user_gesture,
                            info);
-
-  BrowserThread::PostTask(
-      BrowserThread::UI, FROM_HERE,
-      base::Bind(&EventRouter::IncrementInFlightEventsOnUI, browser_context_id,
-                 extension_id, event_id, event_name));
 }
 
 EventRouter::EventRouter(BrowserContext* browser_context,
                          ExtensionPrefs* extension_prefs)
     : browser_context_(browser_context),
       extension_prefs_(extension_prefs),
       extension_registry_observer_(this),
       listeners_(this) {
   registrar_.Add(this, content::NOTIFICATION_RENDERER_PROCESS_TERMINATED,
                  content::NotificationService::AllSources());
@@ skipping 650 matching lines @@
                                      const std::string& extension_id,
                                      const GURL& listener_url,
                                      content::BrowserContext* browser_context)
     : event_name(event_name),
       extension_id(extension_id),
       listener_url(listener_url),
       browser_context(browser_context) {
 }
 
 }  // namespace extensions