Adds ability for WindowManager to create display roots

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 164 matching lines @@
 void Display::OnWillDestroyTree(WindowTree* tree) {
   for (auto it = window_manager_display_root_map_.begin();
        it != window_manager_display_root_map_.end(); ++it) {
     if (it->second->window_manager_state()->window_tree() == tree) {
       window_manager_display_root_map_.erase(it);
       break;
     }
   }
 }
 
+void Display::RemoveWindowManagerDisplayRoot(
+    WindowManagerDisplayRoot* display_root) {
+  for (auto it = window_manager_display_root_map_.begin();
+       it != window_manager_display_root_map_.end(); ++it) {
+    if (it->second == display_root) {
+      window_manager_display_root_map_.erase(it);
+      return;
+    }
+  }
+  NOTREACHED();
+}
+
 void Display::UpdateNativeCursor(mojom::CursorType cursor_id) {
   if (cursor_id != last_cursor_) {
     platform_display_->SetCursorById(cursor_id);
     last_cursor_ = cursor_id;
   }
 }
 
 void Display::SetSize(const gfx::Size& size) {
   platform_display_->SetViewportSize(size);
 }
@@ skipping 193 matching lines @@
 
   UserActivityMonitor* activity_monitor =
       window_server_->GetUserActivityMonitorForUser(
           window_server_->user_id_tracker()->active_id());
   activity_monitor->OnUserActivity();
   return EventDispatchDetails();
 }
 
 }  // namespace ws
 }  // namespace ui