Switch DRM platform to using a separate thread

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

Index: ui/ozone/platform/drm/gpu/gbm_surfaceless.h
diff --git a/ui/ozone/platform/drm/gpu/gbm_surfaceless.h b/ui/ozone/platform/drm/gpu/gbm_surfaceless.h
index 7fa079b5a4c22d4379ead5951f3999451cdd85bc..676ed7be8abdefe399097d6d35bf5d77111e94c8 100644
--- a/ui/ozone/platform/drm/gpu/gbm_surfaceless.h
+++ b/ui/ozone/platform/drm/gpu/gbm_surfaceless.h
@@ -13,8 +13,7 @@ class Size;
 
 namespace ui {
 
-class DrmDeviceManager;
-class DrmWindow;
+class DrmWindowProxy;
 
 // In surfaceless mode drawing and displaying happens directly through
 // NativePixmap buffers. CC would call into SurfaceFactoryOzone to allocate the
@@ -22,7 +21,7 @@ class DrmWindow;
 // presentation.
 class GbmSurfaceless : public SurfaceOzoneEGL {
  public:
-  GbmSurfaceless(DrmWindow* window, DrmDeviceManager* drm_device_manager);
+  GbmSurfaceless(scoped_ptr<DrmWindowProxy> window);
   ~GbmSurfaceless() override;
 
   // SurfaceOzoneEGL:
@@ -34,8 +33,7 @@ class GbmSurfaceless : public SurfaceOzoneEGL {
   bool IsUniversalDisplayLinkDevice() override;
 
  protected:
-  DrmWindow* window_;
-  DrmDeviceManager* drm_device_manager_;
+  scoped_ptr<DrmWindowProxy> window_;
 
   DISALLOW_COPY_AND_ASSIGN(GbmSurfaceless);
 };