Fix GPU service and display initialization race.

services/ui/ws/window_server_delegate.h

 // Copyright 2014 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.
 
 #ifndef SERVICES_UI_WS_WINDOW_SERVER_DELEGATE_H_
 #define SERVICES_UI_WS_WINDOW_SERVER_DELEGATE_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 18 matching lines @@
 class WindowTree;
 class WindowTreeBinding;
 
 class WindowServerDelegate {
  public:
   enum BindingType {
     EMBED,
     WINDOW_MANAGER,
   };
 
+  // WindowServer signal that display initialization can start.
+  virtual void StartDisplayInit() = 0;
+
   // Called once when the AcceleratedWidget of a Display is available.
   virtual void OnFirstDisplayReady();
 
   virtual void OnNoMoreDisplays() = 0;
 
   virtual bool IsTestConfig() const = 0;
 
   // Called when touchscreen coordinate transforms should be updated. For
   // example when displays or touch input devices are added/removed.
   virtual void UpdateTouchTransforms() = 0;
 
   // Creates a WindowTreeBinding. Default implementation returns null, which
   // creates DefaultBinding.
   virtual std::unique_ptr<WindowTreeBinding> CreateWindowTreeBinding(
       BindingType type,
       ws::WindowServer* window_server,
       ws::WindowTree* tree,
       mojom::WindowTreeRequest* tree_request,
       mojom::WindowTreeClientPtr* client);
 
  protected:
   virtual ~WindowServerDelegate() {}
 };
 
 }  // namespace ws
 }  // namespace ui
 
 #endif  // SERVICES_UI_WS_WINDOW_SERVER_DELEGATE_H_