Add a template to handle properly issuing completion callbacks. This fixes

ppapi/proxy/ppb_audio_proxy.cc

Index: ppapi/proxy/ppb_audio_proxy.cc
===================================================================
--- ppapi/proxy/ppb_audio_proxy.cc	(revision 94913)
+++ ppapi/proxy/ppb_audio_proxy.cc	(working copy)
@@ -17,12 +17,13 @@
 #include "ppapi/proxy/ppapi_messages.h"
 #include "ppapi/shared_impl/audio_impl.h"
 #include "ppapi/thunk/ppb_audio_config_api.h"
-#include "ppapi/thunk/ppb_audio_trusted_api.h"
 #include "ppapi/thunk/enter.h"
 #include "ppapi/thunk/resource_creation_api.h"
 #include "ppapi/thunk/thunk.h"
 
-using ::ppapi::thunk::PPB_Audio_API;
+using ppapi::thunk::EnterResourceNoLock;
+using ppapi::thunk::PPB_Audio_API;
+using ppapi::thunk::PPB_AudioConfig_API;
 
 namespace pp {
 namespace proxy {
@@ -42,6 +43,10 @@
   virtual PP_Resource GetCurrentConfig() OVERRIDE;
   virtual PP_Bool StartPlayback() OVERRIDE;
   virtual PP_Bool StopPlayback() OVERRIDE;
+  virtual int32_t OpenTrusted(PP_Resource config_id,
+                              PP_CompletionCallback create_callback) OVERRIDE;
+  virtual int32_t GetSyncSocket(int* sync_socket) OVERRIDE;
+  virtual int32_t GetSharedMemory(int* shm_handle, uint32_t* shm_size) OVERRIDE;
 
  private:
   // Owning reference to the current config object. This isn't actually used,
@@ -95,6 +100,19 @@
   return PP_TRUE;
 }
 
+int32_t Audio::OpenTrusted(PP_Resource config_id,
+                           PP_CompletionCallback create_callback) {
+  return PP_ERROR_NOTSUPPORTED;  // Don't proxy the trusted interface.
+}
+
+int32_t Audio::GetSyncSocket(int* sync_socket) {
+  return PP_ERROR_NOTSUPPORTED;  // Don't proxy the trusted interface.
+}
+
+int32_t Audio::GetSharedMemory(int* shm_handle, uint32_t* shm_size) {
+  return PP_ERROR_NOTSUPPORTED;  // Don't proxy the trusted interface.
+}
+
 namespace {
 
 InterfaceProxy* CreateAudioProxy(Dispatcher* dispatcher,
@@ -147,8 +165,7 @@
   if (!dispatcher)
     return 0;
 
-  ::ppapi::thunk::EnterResourceNoLock< ::ppapi::thunk::PPB_AudioConfig_API>
-      config(config_id, true);
+  EnterResourceNoLock<PPB_AudioConfig_API> config(config_id, true);
   if (config.failed())
     return 0;
 
@@ -193,26 +210,35 @@
       resource_creation.functions()->CreateAudioTrusted(instance_id));
   if (result->is_null())
     return;
-  ::ppapi::thunk::EnterResourceNoLock< ::ppapi::thunk::PPB_AudioTrusted_API>
-      trusted_audio(result->host_resource(), false);
-  if (trusted_audio.failed())
-    return;
 
+  // At this point, we've set the result resource, and this is a sync request.
+  // Anything below this point must issue the AudioChannelConnected callback
+  // to the browser. Since that's an async message, it will be issued back to
+  // the plugin after the Create function returns (which is good because it
+  // would be weird to get a connected message with a failure code for a
+  // resource you haven't finished creating yet).
+  //
+  // The ...ForceCallback class will help ensure the callback is always called.
+  // All error cases must call SetResult on this class.
+  EnterHostFromHostResourceForceCallback<PPB_Audio_API> enter(
+      *result, callback_factory_,
+      &PPB_Audio_Proxy::AudioChannelConnected, *result);
+  if (enter.failed())
+    return;  // When enter fails, it will internally schedule the callback.
+
   // Make an audio config object.
   PP_Resource audio_config_res =
       resource_creation.functions()->CreateAudioConfig(
           instance_id, static_cast<PP_AudioSampleRate>(sample_rate),
           sample_frame_count);
-  if (!audio_config_res)
+  if (!audio_config_res) {
+    enter.SetResult(PP_ERROR_FAILED);
     return;
+  }
 
   // Initiate opening the audio object.
-  CompletionCallback callback = callback_factory_.NewOptionalCallback(
-      &PPB_Audio_Proxy::AudioChannelConnected, *result);
-  int32_t open_error = trusted_audio.object()->OpenTrusted(
-      audio_config_res, callback.pp_completion_callback());
-  if (open_error != PP_OK_COMPLETIONPENDING)
-    callback.Run(open_error);
+  enter.SetResult(enter.object()->OpenTrusted(audio_config_res,
+                                              enter.callback()));
 
   // Clean up the temporary audio config resource we made.
   const PPB_Core* core = static_cast<const PPB_Core*>(
@@ -280,15 +306,14 @@
     IPC::PlatformFileForTransit* foreign_socket_handle,
     base::SharedMemoryHandle* foreign_shared_memory_handle,
     uint32_t* shared_memory_length) {
-  // Get the trusted audio interface which will give us the handles.
-  ::ppapi::thunk::EnterResourceNoLock< ::ppapi::thunk::PPB_AudioTrusted_API>
-      trusted_audio(resource.host_resource(), false);
-  if (trusted_audio.failed())
+  // Get the audio interface which will give us the handles.
+  EnterResourceNoLock<PPB_Audio_API> enter(resource.host_resource(), false);
+  if (enter.failed())
     return PP_ERROR_NOINTERFACE;
 
   // Get the socket handle for signaling.
   int32_t socket_handle;
-  int32_t result = trusted_audio.object()->GetSyncSocket(&socket_handle);
+  int32_t result = enter.object()->GetSyncSocket(&socket_handle);
   if (result != PP_OK)
     return result;
 
@@ -300,8 +325,8 @@
 
   // Get the shared memory for the buffer.
   int shared_memory_handle;
-  result = trusted_audio.object()->GetSharedMemory(&shared_memory_handle,
-                                                   shared_memory_length);
+  result = enter.object()->GetSharedMemory(&shared_memory_handle,
+                                           shared_memory_length);
   if (result != PP_OK)
     return result;