Make ozone/drm/mojo more immune to startup races

ui/ozone/platform/drm/cursor_proxy_mojo.h

 // 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.
 
 #ifndef UI_OZONE_PLATFORM_DRM_CURSOR_PROXY_MOJO_H_
 #define UI_OZONE_PLATFORM_DRM_CURSOR_PROXY_MOJO_H_
 
 #include "ui/gfx/native_widget_types.h"
 #include "ui/ozone/platform/drm/gpu/inter_thread_messaging_proxy.h"
 #include "ui/ozone/platform/drm/host/drm_cursor.h"
+#include "ui/ozone/platform/drm/host/gpu_thread_observer.h"
 #include "ui/ozone/public/interfaces/device_cursor.mojom.h"
 
 namespace service_manager {
 class Connector;
 }
 
 namespace ui {
 
 // Ozone requires a IPC from the browser (or mus-ws) process to the gpu (or
 // mus-gpu) process to control the mouse pointer. This class provides mouse
 // pointer control via Mojo-style IPC. This code runs only in the mus-ws (i.e.
 // it's the client) and sends mouse pointer control messages to a less
 // priviledged process.
-class CursorProxyMojo : public DrmCursorProxy {
+class CursorProxyMojo : public DrmCursorProxy, public GpuThreadObserver {
  public:
   explicit CursorProxyMojo(service_manager::Connector* connector);
   ~CursorProxyMojo() override;
 
  private:
   // DrmCursorProxy.
   void CursorSet(gfx::AcceleratedWidget window,
                  const std::vector<SkBitmap>& bitmaps,
                  const gfx::Point& point,
                  int frame_delay_ms) override;
   void Move(gfx::AcceleratedWidget window, const gfx::Point& point) override;
   void InitializeOnEvdev() override;
 
+  // GpuThreadObserver
+  void OnGpuProcessLaunched() override;
+  void OnGpuThreadReady() override;
+  void OnGpuThreadRetired() override;
+
   std::unique_ptr<service_manager::Connector> connector_;
 
   // Mojo implementation of the DrmCursorProxy.
   ui::ozone::mojom::DeviceCursorPtr main_cursor_ptr_;
   ui::ozone::mojom::DeviceCursorPtr evdev_cursor_ptr_;
 
   base::PlatformThreadRef evdev_ref_;
+
+  bool have_gpu_thread_ = false;
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_DRM_CURSOR_PROXY_MOJO_H_