[mojo] Implement pipe fusion API

mojo/public/cpp/bindings/interface_request.h

 // Copyright 2014 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.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_INTERFACE_REQUEST_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_INTERFACE_REQUEST_H_
 
 #include <utility>
 
 #include "mojo/public/cpp/bindings/interface_ptr.h"
@@ skipping 99 matching lines @@
 //   collector->RegisterSource(std::move(source));
 //   CreateSource(std::move(source_request));  // Create implementation locally.
 //
 template <typename Interface>
 InterfaceRequest<Interface> GetProxy(InterfacePtr<Interface>* ptr) {
   MessagePipe pipe;
   ptr->Bind(InterfacePtrInfo<Interface>(std::move(pipe.handle0), 0u));
   return MakeRequest<Interface>(std::move(pipe.handle1));
 }
 
+// Fuses an InterfaceRequest<T> endpoint with an InterfacePtr<T> endpoint.
+// Returns |true| on success or |false| on failure. Note that both arguments
+// are invalidated regardless of the result.
+template <typename Interface>
+bool FuseProxy(InterfaceRequest<Interface> *request,

[yzshen1, 2016/03/10 23:49:03]

How about the following signature:

bool FuseInterface(InterfaceRequset<Interface> request,
                   InterfacePtrInfo<Interface> ptr_info);

- The request and ptr are "symmetric" in this case, so it seems unnecessary to
have "proxy" in the name.
- Pass them by value because they are invalidated anyway.
- Maybe PtrInfo is better than Ptr here?

[Ken Rockot(use gerrit already), 2016/03/11 00:32:46]

Done

+               InterfacePtr<Interface>* proxy) {
+  ScopedMessagePipeHandle handle0 = request->PassMessagePipe();
+  ScopedMessagePipeHandle handle1 = proxy->PassInterface().PassHandle();
+  MojoResult result = FuseMessagePipes(&handle0, &handle1);
+  return result == MOJO_RESULT_OK;
+}
+
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_INTERFACE_REQUEST_H_