Switch DRM platform to using a separate thread

ui/ozone/platform/drm/gpu/gbm_surface_factory.h

Index: ui/ozone/platform/drm/gpu/gbm_surface_factory.h
diff --git a/ui/ozone/platform/drm/gpu/gbm_surface_factory.h b/ui/ozone/platform/drm/gpu/gbm_surface_factory.h
index 0aa433d8c5fbe8b4bb4541c95562e3e3ba4ba65a..88dc7a39265c42c03e59e292eb674a13547d4832 100644
--- a/ui/ozone/platform/drm/gpu/gbm_surface_factory.h
+++ b/ui/ozone/platform/drm/gpu/gbm_surface_factory.h
@@ -10,20 +10,15 @@
 
 namespace ui {
 
-class DrmDeviceManager;
-class DrmWindow;
+class DrmThread;
 class GbmDevice;
-class ScreenManager;
 
 class GbmSurfaceFactory : public SurfaceFactoryOzone {
  public:
-  GbmSurfaceFactory();
+  GbmSurfaceFactory(DrmThread* drm_thread);
   ~GbmSurfaceFactory() override;
 
-  void InitializeGpu(DrmDeviceManager* drm_device_manager,
-                     ScreenManager* screen_manager);
-
-  // DrmSurfaceFactory:
+  // SurfaceFactoryOzone:
   intptr_t GetNativeDisplay() override;
   const int32_t* GetEGLSurfaceProperties(const int32_t* desired_list) override;
   bool LoadEGLGLES2Bindings(
@@ -44,11 +39,10 @@ class GbmSurfaceFactory : public SurfaceFactoryOzone {
  private:
   scoped_refptr<GbmDevice> GetGbmDevice(gfx::AcceleratedWidget widget);
 
-  DrmDeviceManager* drm_device_manager_;  // Not owned.
-  ScreenManager* screen_manager_;         // Not owned.
-
   base::ThreadChecker thread_checker_;
 
+  DrmThread* drm_thread_;
+
   DISALLOW_COPY_AND_ASSIGN(GbmSurfaceFactory);
 };