PPAPI: Make GetProxiedInterface not re-enter the plugin

ppapi/proxy/ppb_video_decoder_proxy.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/ppb_video_decoder_proxy.h"
 
 #include "base/logging.h"
 #include "gpu/command_buffer/client/gles2_implementation.h"
+#include "ppapi/c/dev/ppp_video_decoder_dev.h"
 #include "ppapi/proxy/enter_proxy.h"
 #include "ppapi/proxy/plugin_dispatcher.h"
 #include "ppapi/proxy/ppapi_messages.h"
 #include "ppapi/proxy/ppb_buffer_proxy.h"
 #include "ppapi/proxy/ppb_graphics_3d_proxy.h"
 #include "ppapi/thunk/enter.h"
 #include "ppapi/thunk/resource_creation_api.h"
 #include "ppapi/thunk/thunk.h"
 
 using ppapi::thunk::EnterResourceNoLock;
@@ skipping 169 matching lines @@
     PP_VideoDecoder_Profile profile) {
   PluginDispatcher* dispatcher = PluginDispatcher::GetForInstance(instance);
   // Dispatcher is null if it cannot find the instance passed to it (i.e. if the
   // client passes in an invalid instance).
   if (!dispatcher)
     return 0;
 
   if (!dispatcher->preferences().is_accelerated_video_decode_enabled)
     return 0;
 
+  // We must get the plugin interface now, prior to doing Create synchronously.
+  // Otherwise, the browser will try to get the interface via a re-entrant
+  // sync message back to us, which would deadlock.
+  const std::string if_name = PPP_VIDEODECODER_DEV_INTERFACE_0_11;
+  if (!dispatcher->GetPluginInterface(if_name))
+    return 0;
+  dispatcher->Send(new PpapiHostMsg_PluginSupportsInterface(if_name));

[piman, 2014/11/06 23:52:38]

This works, but mostly my thinking was that PPB_VideoDecoder_Impl would simply
query the ppp_videodecoder_ interface before any of the calls that needs it
(which shouldn't re-enter). That way you wouldn't need to add an extra IPC.

+
   EnterResourceNoLock<PPB_Graphics3D_API> enter_context(graphics_context,
                                                         true);
   if (enter_context.failed())
     return 0;
 
   Graphics3D* context = static_cast<Graphics3D*>(enter_context.object());
 
   HostResource result;
   dispatcher->Send(new PpapiHostMsg_PPBVideoDecoder_Create(
       API_ID_PPB_VIDEO_DECODER_DEV, instance,
@@ skipping 106 matching lines @@
 
 void PPB_VideoDecoder_Proxy::OnMsgResetACK(
     const HostResource& decoder, int32_t result) {
   EnterPluginFromHostResource<PPB_VideoDecoder_Dev_API> enter(decoder);
   if (enter.succeeded())
     static_cast<VideoDecoder*>(enter.object())->ResetACK(result);
 }
 
 }  // namespace proxy
 }  // namespace ppapi