WIP: A couple of more ChannelMojo speedup ideas

ipc/mojo/ipc_message_pipe_reader.h

Index: ipc/mojo/ipc_message_pipe_reader.h
diff --git a/ipc/mojo/ipc_message_pipe_reader.h b/ipc/mojo/ipc_message_pipe_reader.h
index 74de71b80ba87ef9f02d159409c6e8efd70bc5c1..ad14fe33afff4afb670d8f6e274f5ac21b3ca0ce 100644
--- a/ipc/mojo/ipc_message_pipe_reader.h
+++ b/ipc/mojo/ipc_message_pipe_reader.h
@@ -10,14 +10,13 @@
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "ipc/ipc_message.h"
+#include "ipc/mojo/async_handle_waiter.h"
 #include "third_party/mojo/src/mojo/public/c/environment/async_waiter.h"
 #include "third_party/mojo/src/mojo/public/cpp/system/core.h"
 
 namespace IPC {
 namespace internal {
 
-class AsyncHandleWaiter;
-
 // A helper class to handle bytestream directly over mojo::MessagePipe
 // in template-method pattern. MessagePipeReader manages the lifetime
 // of given MessagePipe and participates the event loop, and
@@ -32,7 +31,7 @@ class AsyncHandleWaiter;
 //
 // MessageReader has to be used in IO thread. It isn't thread-safe.
 //
-class MessagePipeReader {
+class MessagePipeReader : public AsyncHandleWaiter::Delegate {
  public:
   class Delegate {
    public:
@@ -90,8 +89,11 @@ class MessagePipeReader {
   void OnPipeClosed();
   void OnPipeError(MojoResult error);
 
+  // AsyncHandleWaiter::Delegate implementations
+  void PipeIsReady(MojoResult wait_result) override;
+  void MessageWasArrived(const void* bytes, uint32_t num_bytes) override;
+
   MojoResult ReadMessageBytes();
-  void PipeIsReady(MojoResult wait_result);
   void ReadAvailableMessages();
 
   std::vector<char>  data_buffer_;