Gracefully handle multiple Flush/Reset/Decode with same id

ppapi/proxy/ppb_video_decoder_proxy.cc

 // Copyright (c) 2011 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/proxy/enter_proxy.h"
 #include "ppapi/proxy/plugin_dispatcher.h"
@@ skipping 78 matching lines @@
 }
 
 int32_t VideoDecoder::Decode(
     const PP_VideoBitstreamBuffer_Dev* bitstream_buffer,
     PP_CompletionCallback callback) {
   ppapi::thunk::EnterResourceNoLock<PPB_Buffer_API>
       enter_buffer(bitstream_buffer->data, true);
   if (enter_buffer.failed())
     return PP_ERROR_BADRESOURCE;
 
-  SetBitstreamBufferCallback(bitstream_buffer->id, callback);
+  if (!SetBitstreamBufferCallback(bitstream_buffer->id, callback))
+    return PP_ERROR_BADARGUMENT;
 
   Buffer* ppb_buffer =
       static_cast<Buffer*>(enter_buffer.object());
   HostResource host_buffer = ppb_buffer->host_resource();
 
   FlushCommandBuffer();
   GetDispatcher()->Send(new PpapiHostMsg_PPBVideoDecoder_Decode(
       INTERFACE_ID_PPB_VIDEO_DECODER_DEV, host_resource(),
       host_buffer, bitstream_buffer->id,
       bitstream_buffer->size));
@@ skipping 10 matching lines @@
           INTERFACE_ID_PPB_VIDEO_DECODER_DEV, host_resource(), buffer_list));
 }
 
 void VideoDecoder::ReusePictureBuffer(int32_t picture_buffer_id) {
   FlushCommandBuffer();
   GetDispatcher()->Send(new PpapiHostMsg_PPBVideoDecoder_ReusePictureBuffer(
       INTERFACE_ID_PPB_VIDEO_DECODER_DEV, host_resource(), picture_buffer_id));
 }
 
 int32_t VideoDecoder::Flush(PP_CompletionCallback callback) {
-  SetFlushCallback(callback);
+  if (!SetFlushCallback(callback))
+    return PP_ERROR_INPROGRESS;
 
   FlushCommandBuffer();
   GetDispatcher()->Send(new PpapiHostMsg_PPBVideoDecoder_Flush(
       INTERFACE_ID_PPB_VIDEO_DECODER_DEV, host_resource()));
   return PP_OK_COMPLETIONPENDING;
 }
 
 int32_t VideoDecoder::Reset(PP_CompletionCallback callback) {
-  SetResetCallback(callback);
+  if (!SetResetCallback(callback))
+    return PP_ERROR_INPROGRESS;
 
   FlushCommandBuffer();
   GetDispatcher()->Send(new PpapiHostMsg_PPBVideoDecoder_Reset(
       INTERFACE_ID_PPB_VIDEO_DECODER_DEV, host_resource()));
   return PP_OK_COMPLETIONPENDING;
 }
 
 void VideoDecoder::Destroy() {
   FlushCommandBuffer();
   GetDispatcher()->Send(new PpapiHostMsg_PPBVideoDecoder_Destroy(
@@ skipping 204 matching lines @@
 
 void PPB_VideoDecoder_Proxy::OnMsgResetACK(
     const HostResource& decoder, int32_t result) {
   EnterPluginFromHostResource<PPB_VideoDecoder_API> enter(decoder);
   if (enter.succeeded())
     static_cast<VideoDecoder*>(enter.object())->ResetACK(result);
 }
 
 }  // namespace proxy
 }  // namespace pp