Only send the FrameSinkId to client when it is necessary

ui/aura/test/mus/window_tree_client_private.cc

 // Copyright 2016 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/test/mus/window_tree_client_private.h"
 
 #include "ui/aura/mus/window_port_mus.h"
 #include "ui/aura/mus/window_tree_client.h"
 #include "ui/aura/mus/window_tree_host_mus_init_params.h"
 #include "ui/aura/window.h"
@@ skipping 13 matching lines @@
 
 void WindowTreeClientPrivate::OnEmbed(ui::mojom::WindowTree* window_tree) {
   ui::mojom::WindowDataPtr root_data(ui::mojom::WindowData::New());
   root_data->parent_id = 0;
   root_data->window_id = next_window_id_++;
   root_data->visible = true;
   const int64_t display_id = 1;
   const Id focused_window_id = 0;
   tree_client_impl_->OnEmbedImpl(window_tree, 1, std::move(root_data),
                                  display_id, focused_window_id, true,
-                                 cc::FrameSinkId(1, 1), base::nullopt);
+                                 base::nullopt);
 }
 
 WindowTreeHostMus* WindowTreeClientPrivate::CallWmNewDisplayAdded(
     const display::Display& display) {
   ui::mojom::WindowDataPtr root_data(ui::mojom::WindowData::New());
   root_data->parent_id = 0;
   root_data->window_id = next_window_id_++;
   root_data->visible = true;
   root_data->bounds = gfx::Rect(display.bounds().size());
   const bool parent_drawn = true;
   return CallWmNewDisplayAdded(display, std::move(root_data), parent_drawn);
 }
 
 WindowTreeHostMus* WindowTreeClientPrivate::CallWmNewDisplayAdded(
     const display::Display& display,
     ui::mojom::WindowDataPtr root_data,
     bool parent_drawn) {
-  return tree_client_impl_->WmNewDisplayAddedImpl(
-      display, std::move(root_data), parent_drawn, cc::FrameSinkId(1, 1),
-      base::nullopt);
+  return tree_client_impl_->WmNewDisplayAddedImpl(display, std::move(root_data),
+                                                  parent_drawn, base::nullopt);
 }
 
 void WindowTreeClientPrivate::CallOnWindowInputEvent(
     Window* window,
     std::unique_ptr<ui::Event> event) {
   const uint32_t event_id = 0u;
   const uint32_t observer_id = 0u;
   const int64_t display_id = 0;
   tree_client_impl_->OnWindowInputEvent(
       event_id, WindowPortMus::Get(window)->server_id(), display_id,
@@ skipping 42 matching lines @@
 bool WindowTreeClientPrivate::HasPointerWatcher() {
   return tree_client_impl_->has_pointer_watcher_;
 }
 
 Window* WindowTreeClientPrivate::GetWindowByServerId(Id id) {
   WindowMus* window = tree_client_impl_->GetWindowByServerId(id);
   return window ? window->GetWindow() : nullptr;
 }
 
 }  // namespace aura