WIP: Propagate SurfaceID up window tree hierarchy

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 267 matching lines @@
   display_root->window_manager_state_ = window_manager_state;
   const bool is_active =
       factory->user_id() == window_server_->user_id_tracker()->active_id();
   display_root->root()->SetVisible(is_active);
   window_manager_state->window_tree()->AddRootForWindowManager(
       display_root->root());
   window_manager_state->AddWindowManagerDisplayRoot(
       std::move(display_root_ptr));
 }
 
+ServerWindow* Display::GetActiveRootWindow() {
+  WindowManagerDisplayRoot* display_root = GetActiveWindowManagerDisplayRoot();
+  if (display_root)
+    return display_root->root();
+  return nullptr;
+}
+
 ServerWindow* Display::GetRootWindow() {
   return root_.get();
 }
 
 bool Display::IsInHighContrastMode() {
   return window_server_->IsActiveUserInHighContrastMode();
 }
 
 void Display::OnEvent(const ui::Event& event) {
   WindowManagerDisplayRoot* display_root = GetActiveWindowManagerDisplayRoot();
@@ skipping 127 matching lines @@
 }
 
 void Display::OnWindowManagerWindowTreeFactoryReady(
     WindowManagerWindowTreeFactory* factory) {
   if (!binding_)
     CreateWindowManagerDisplayRootFromFactory(factory);
 }
 
 }  // namespace ws
 }  // namespace ui