Only send the FrameSinkId to client when it is necessary

ui/aura/mus/window_tree_host_mus.cc

 // 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.
 
 #include "ui/aura/mus/window_tree_host_mus.h"
 
 #include "base/memory/ptr_util.h"
 #include "ui/aura/env.h"
 #include "ui/aura/mus/input_method_mus.h"
 #include "ui/aura/mus/window_port_mus.h"
@@ skipping 34 matching lines @@
     bounds_in_pixels = display_init_params_->viewport_metrics.bounds_in_pixels;
   window()->SetProperty(kWindowTreeHostMusKey, this);
   // TODO(sky): find a cleaner way to set this! Better solution is to likely
   // have constructor take aura::Window.
   WindowPortMus* window_mus = WindowPortMus::Get(window());
   window_mus->window_ = window();
   // Apply the properties before initializing the window, that way the server
   // seems them at the time the window is created.
   for (auto& pair : init_params.properties)
     window_mus->SetPropertyFromServer(pair.first, &pair.second);
-  // TODO(fsamuel): Once the display compositor is decoupled from the browser
-  // process then ui::Compositor will not a cc::FrameSinkId.
-  CreateCompositor(init_params.frame_sink_id);
+  CreateCompositor(cc::FrameSinkId());
   gfx::AcceleratedWidget accelerated_widget;
 // We need accelerated widget numbers to be different for each
 // window and fit in the smallest sizeof(AcceleratedWidget) uint32_t
 // has this property.
 #if defined(OS_WIN) || defined(OS_ANDROID)
   accelerated_widget =
       reinterpret_cast<gfx::AcceleratedWidget>(accelerated_widget_count++);
 #else
   accelerated_widget =
       static_cast<gfx::AcceleratedWidget>(accelerated_widget_count++);
@@ skipping 11 matching lines @@
   if (!init_params.use_classic_ime) {
     input_method_ = base::MakeUnique<InputMethodMus>(this, window());
     input_method_->Init(init_params.window_tree_client->connector());
     SetSharedInputMethod(input_method_.get());
   }
 
   compositor()->SetHostHasTransparentBackground(true);
 
   // Mus windows are assumed hidden.
   compositor()->SetVisible(false);
-
-  if (init_params.frame_sink_id.is_valid())
-    window_mus->SetFrameSinkIdFromServer(init_params.frame_sink_id);
 }
 
 WindowTreeHostMus::~WindowTreeHostMus() {
   DestroyCompositor();
   DestroyDispatcher();
 }
 
 // static
 WindowTreeHostMus* WindowTreeHostMus::ForWindow(aura::Window* window) {
   if (!window)
@@ skipping 104 matching lines @@
 void WindowTreeHostMus::MoveCursorToScreenLocationInPixels(
     const gfx::Point& location_in_pixels) {
   // TODO: this needs to message the server http://crbug.com/693340. Setting
   // the location is really only appropriate in tests, outside of tests this
   // value is ignored.
   NOTIMPLEMENTED();
   Env::GetInstance()->set_last_mouse_location(location_in_pixels);
 }
 
 }  // namespace aura