cc:: Add remote mode to the compositor

cc/proto/compositor_message_to_impl.proto

+// Copyright 2015 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.
+
+syntax = "proto2";
+
+option optimize_for = LITE_RUNTIME;
+
+import "layer_tree_settings.proto";
+
+package cc.proto;
+
+// Control messages sent to the impl side of the compositor on the client.
+message CompositorMessageToImpl {
+  enum Type {
+    Unknown = 0;
+    InitializeImpl = 1;
+    CloseImpl = 2;
+    MainThreadHasStoppedFlingingOnImpl = 3;
+  }
+
+  optional Type message_type = 1;
+  optional InitializeImpl initialize_impl_message = 2;
+}
+
+message InitializeImpl {
+  optional LayerTreeSettings layer_tree_settings = 1;
+}