[mojo] Implement pipe fusion API

mojo/public/cpp/bindings/interface_request.h

Index: mojo/public/cpp/bindings/interface_request.h
diff --git a/mojo/public/cpp/bindings/interface_request.h b/mojo/public/cpp/bindings/interface_request.h
index f67566d2d0ef76e2537eafe22b0e31f55f42a649..92b08c814e50e857e013c9d4ca0bf18e2de724ae 100644
--- a/mojo/public/cpp/bindings/interface_request.h
+++ b/mojo/public/cpp/bindings/interface_request.h
@@ -117,6 +117,18 @@ InterfaceRequest<Interface> GetProxy(InterfacePtr<Interface>* ptr) {
   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_