Add trace events for PPB audio callbacks.

ppapi/shared_impl/ppb_audio_shared.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/shared_impl/ppb_audio_shared.h"
 
+#include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "ppapi/nacl_irt/public/irt_ppapi.h"
 #include "ppapi/shared_impl/ppapi_globals.h"
 #include "ppapi/shared_impl/ppb_audio_config_shared.h"
 #include "ppapi/shared_impl/proxy_lock.h"
 
 namespace ppapi {
 
 namespace {
 bool g_nacl_mode = false;
@@ skipping 188 matching lines @@
 void PPB_Audio_Shared::Run() {
   int pending_data = 0;
   while (sizeof(pending_data) ==
          socket_->Receive(&pending_data, sizeof(pending_data))) {
     // |buffer_index_| must track the number of Receive() calls.  See the Send()
     // call below for why this is important.
     ++buffer_index_;
     if (pending_data < 0)
       break;
 
-    PP_TimeDelta latency =
-        static_cast<double>(pending_data) / bytes_per_second_;
-    callback_.Run(
-        client_buffer_.get(), client_buffer_size_bytes_, latency, user_data_);
+    {
+      TRACE_EVENT0("audio", "PPB_Audio_Shared::FireRenderCallback");
+      PP_TimeDelta latency =
+          static_cast<double>(pending_data) / bytes_per_second_;
+      callback_.Run(
+          client_buffer_.get(), client_buffer_size_bytes_, latency, user_data_);
+    }
 
     // Deinterleave the audio data into the shared memory as floats.
     audio_bus_->FromInterleaved(client_buffer_.get(),
                                 audio_bus_->frames(),
                                 kBitsPerAudioOutputSample / 8);
 
     // Let the other end know which buffer we just filled.  The buffer index is
     // used to ensure the other end is getting the buffer it expects.  For more
     // details on how this works see AudioSyncReader::WaitUntilDataIsReady().
     size_t bytes_sent = socket_->Send(&buffer_index_, sizeof(buffer_index_));
     if (bytes_sent != sizeof(buffer_index_))
       break;
   }
 }
 
 }  // namespace ppapi