Pass root ServerWindow id to FrameGenerator.

services/ui/ws/display.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 "services/ui/ws/display.h"
 
 #include <set>
 #include <utility>
 #include <vector>
 
@@ skipping 15 matching lines @@
 #include "services/ui/ws/window_server.h"
 #include "services/ui/ws/window_server_delegate.h"
 #include "services/ui/ws/window_tree.h"
 #include "services/ui/ws/window_tree_binding.h"
 #include "ui/base/cursor/cursor.h"
 
 namespace ui {
 namespace ws {
 
 Display::Display(WindowServer* window_server,
-                 const PlatformDisplayInitParams& platform_display_init_params)
-    : window_server_(window_server),
-      platform_display_(PlatformDisplay::Create(platform_display_init_params)),
-      last_cursor_(mojom::Cursor::CURSOR_NULL) {
+                 PlatformDisplayInitParams init_params)

[Fady Samuel, 2016/10/24 21:53:22]

This is more or less the same in terms of cost, but I generally prefer passing
by const ref, copying locally and updating.

[kylechar, 2016/10/25 18:15:01]

Done.

+    : window_server_(window_server), last_cursor_(mojom::Cursor::CURSOR_NULL) {
+  // Create the root ServerWindow and pass the window id along.
+  CreateRootWindow(init_params.metrics.bounds.size());
+  init_params.root_window_id = root_->id();
+
+  platform_display_.reset(PlatformDisplay::Create(init_params));
   platform_display_->Init(this);
 
   window_server_->window_manager_window_tree_factory_set()->AddObserver(this);
   window_server_->user_id_tracker()->AddObserver(this);
 }
 
 Display::~Display() {
   window_server_->user_id_tracker()->RemoveObserver(this);
 
   window_server_->window_manager_window_tree_factory_set()->RemoveObserver(
@@ skipping 346 matching lines @@
 }
 
 void Display::OnWindowManagerWindowTreeFactoryReady(
     WindowManagerWindowTreeFactory* factory) {
   if (!binding_)
     CreateWindowManagerDisplayRootFromFactory(factory);
 }
 
 }  // namespace ws
 }  // namespace ui