Switch DRM platform to using a separate thread

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

Index: ui/ozone/platform/drm/gpu/drm_window.h
diff --git a/ui/ozone/platform/drm/gpu/drm_window.h b/ui/ozone/platform/drm/gpu/drm_window.h
index c918499ed5ff19bb8e2a48e9b45196f7a2511b8f..1616dd8b7c2a150454625798bea636881797ba49 100644
--- a/ui/ozone/platform/drm/gpu/drm_window.h
+++ b/ui/ozone/platform/drm/gpu/drm_window.h
@@ -28,6 +28,7 @@ class Rect;
 namespace ui {
 
 class DrmBuffer;
+class DrmDevice;
 class DrmDeviceManager;
 class HardwareDisplayController;
 struct OverlayCheck_Params;
@@ -43,7 +44,7 @@ class ScreenManager;
 //
 // If there's no display whose bounds match the window's, the window is
 // disconnected and its contents will not be visible to the user.
-class OZONE_EXPORT DrmWindow {
+class OZONE_EXPORT DrmWindow : public base::SupportsWeakPtr<DrmWindow> {
  public:
   DrmWindow(gfx::AcceleratedWidget widget,
             DrmDeviceManager* device_manager,
@@ -64,6 +65,8 @@ class OZONE_EXPORT DrmWindow {
   // not cache the result as the controller may change as the window is moved.
   HardwareDisplayController* GetController();
 
+  scoped_refptr<DrmDevice> GetAllocationDrmDevice() const;
+
   void SetController(HardwareDisplayController* controller);
 
   // Called when the window is resized/moved.
@@ -89,7 +92,7 @@ class OZONE_EXPORT DrmWindow {
   // is once again ready.
   void QueueOverlayPlane(const OverlayPlane& plane);
 
-  bool SchedulePageFlip(bool is_sync, const SwapCompletionCallback& callback);
+  void SchedulePageFlip(bool is_sync, const SwapCompletionCallback& callback);
   bool TestPageFlip(const std::vector<OverlayCheck_Params>& planes,
                     ScanoutBufferGenerator* buffer_generator);
 
@@ -99,6 +102,8 @@ class OZONE_EXPORT DrmWindow {
   void GetVSyncParameters(
       const gfx::VSyncProvider::UpdateVSyncCallback& callback) const;
 
+  bool IsDisplayedOnUniversalDisplayLinkDevice() const;
+
  private:
   // Draw the last set cursor & update the cursor plane.
   void ResetCursor(bool bitmap_only);