WIP: A couple of more ChannelMojo speedup ideas

ipc/mojo/async_handle_waiter.h

Index: ipc/mojo/async_handle_waiter.h
diff --git a/ipc/mojo/async_handle_waiter.h b/ipc/mojo/async_handle_waiter.h
index 55acb3eb8e2ecdec369dd56420a678b2da2be810..9b0b4434024954c67398a7bfd9ac0a4aa607917f 100644
--- a/ipc/mojo/async_handle_waiter.h
+++ b/ipc/mojo/async_handle_waiter.h
@@ -27,16 +27,27 @@ class IPC_MOJO_EXPORT AsyncHandleWaiter {
  public:
   class Context;
 
-  explicit AsyncHandleWaiter(base::Callback<void(MojoResult)> callback);
+  class Delegate {
+   public:
+    virtual void PipeIsReady(MojoResult result) = 0;
+    virtual void MessageWasArrived(const void* bytes, uint32_t num_bytes) = 0;
+  };
+
+  explicit AsyncHandleWaiter(Delegate* delegate);
   ~AsyncHandleWaiter();
 
+  void SetMessageCallback(MojoHandle handle);
+  void ClearMessageCallback(MojoHandle handle);
   MojoResult Wait(MojoHandle handle, MojoHandleSignals signals);
 
  private:
   void InvokeCallback(MojoResult result);
+  void InvokeMessageCallback(const void* bytes, uint32_t num_bytes);
 
   scoped_refptr<Context> context_;
-  base::Callback<void(MojoResult)> callback_;
+  Delegate* delegate_;
+  base::Callback<void(MojoResult)> context_callback_;
+  base::Callback<bool(const void*, uint32_t)> context_message_callback_;
   base::WeakPtrFactory<AsyncHandleWaiter> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AsyncHandleWaiter);