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 d373f155f82ca7eb1feadb91f02c06886ad6d1e2..995dd941d6bc4ebc8e49ce5f22347ae81168ddb7 100644
--- a/ui/ozone/platform/drm/gpu/gbm_surface_factory.h
+++ b/ui/ozone/platform/drm/gpu/gbm_surface_factory.h
@@ -9,19 +9,14 @@
 
 namespace ui {
 
-class DrmDeviceManager;
-class DrmWindow;
+class DrmThread;
 class GbmDevice;
-class ScreenManager;
 
 class GbmSurfaceFactory : public DrmSurfaceFactory {
  public:
-  GbmSurfaceFactory(bool allow_surfaceless);
+  GbmSurfaceFactory(bool allow_surfaceless, DrmThread* drm_thread);
   ~GbmSurfaceFactory() override;
 
-  void InitializeGpu(DrmDeviceManager* drm_device_manager,
-                     ScreenManager* screen_manager);
-
   // DrmSurfaceFactory:
   intptr_t GetNativeDisplay() override;
   const int32_t* GetEGLSurfaceProperties(const int32_t* desired_list) override;
@@ -46,8 +41,6 @@ class GbmSurfaceFactory : public DrmSurfaceFactory {
 
   bool allow_surfaceless_;
 
-  DrmDeviceManager* drm_device_manager_;  // Not owned.
-
   DISALLOW_COPY_AND_ASSIGN(GbmSurfaceFactory);
 };