Add async trace events to trace progress of IPC messages

ipc/ipc_channel_reader.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 "ipc/ipc_channel_reader.h"
 
 namespace IPC {
 namespace internal {
 
 ChannelReader::ChannelReader(Listener* listener) : listener_(listener) {
@@ skipping 51 matching lines @@
 
   // Dispatch all complete messages in the data buffer.
   while (p < end) {
     const char* message_tail = Message::FindNext(p, end);
     if (message_tail) {
       int len = static_cast<int>(message_tail - p);
       Message m(p, len);
       if (!WillDispatchInputMessage(&m))
         return false;
 
+      m.TraceMessageStep();
       if (IsHelloMessage(m))
         HandleHelloMessage(m);
       else
         listener_->OnMessageReceived(m);
       p = message_tail;
     } else {
       // Last message is partial.
       break;
     }
   }
 
   // Save any partial data in the overflow buffer.
   input_overflow_buf_.assign(p, end - p);
 
   if (input_overflow_buf_.empty() && !DidEmptyInputBuffers())
     return false;
   return true;
 }
 
 
 }  // namespace internal
 }  // namespace IPC