Enable pepper threading by default.

ppapi/proxy/plugin_dispatcher.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 "ppapi/proxy/plugin_dispatcher.h"
 
 #include <map>
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
@@ skipping 182 matching lines @@
     // Synchronous messages might be re-entrant, so we need to drop the lock.
     ProxyAutoUnlock unlock;
     return Dispatcher::Send(msg);
   }
   return Dispatcher::Send(msg);
 }
 
 bool PluginDispatcher::OnMessageReceived(const IPC::Message& msg) {
   // We need to grab the proxy lock to ensure that we don't collide with the
   // plugin making pepper calls on a different thread.
   ProxyAutoLock lock;

[dmichael (off chromium), 2012/11/06 19:24:10]

Shouldn't this lock cover it? Or can we get to OnMsgResourceReply some other
way?

   TRACE_EVENT2("ppapi proxy", "PluginDispatcher::OnMessageReceived",
                "Class", IPC_MESSAGE_ID_CLASS(msg.type()),
                "Line", IPC_MESSAGE_ID_LINE(msg.type()));
 
   if (msg.routing_id() == MSG_ROUTING_CONTROL) {
     // Handle some plugin-specific control messages.
     bool handled = true;
     IPC_BEGIN_MESSAGE_MAP(PluginDispatcher, msg)
       IPC_MESSAGE_HANDLER(PpapiPluginMsg_ResourceReply, OnMsgResourceReply)
       IPC_MESSAGE_HANDLER(PpapiMsg_SupportsInterface, OnMsgSupportsInterface)
@@ skipping 53 matching lines @@
 
 thunk::ResourceCreationAPI* PluginDispatcher::GetResourceCreationAPI() {
   return static_cast<ResourceCreationProxy*>(
       GetInterfaceProxy(API_ID_RESOURCE_CREATION));
 }
 
 // static
 void PluginDispatcher::DispatchResourceReply(
     const ppapi::proxy::ResourceMessageReplyParams& reply_params,
     const IPC::Message& nested_msg) {
+  // We need to grab the proxy lock to ensure that we don't collide with the
+  // plugin making pepper calls on a different thread.
+  ProxyAutoLock lock;
+
   Resource* resource = PpapiGlobals::Get()->GetResourceTracker()->GetResource(
       reply_params.pp_resource());
   if (!resource) {
     if (reply_params.sequence())
       NOTREACHED();
     return;
   }
   resource->OnReplyReceived(reply_params, nested_msg);
 }
 
@@ skipping 44 matching lines @@
   // once they're set. The user will have to restart to get new font prefs
   // propogated to plugins.
   if (!received_preferences_) {
     received_preferences_ = true;
     preferences_ = prefs;
   }
 }
 
 }  // namespace proxy
 }  // namespace ppapi