ozone: dri: add synchronous SwapBuffers support on surfaceless

ui/ozone/platform/dri/hardware_display_controller.h

Index: ui/ozone/platform/dri/hardware_display_controller.h
diff --git a/ui/ozone/platform/dri/hardware_display_controller.h b/ui/ozone/platform/dri/hardware_display_controller.h
index e2db520ed8538c42096ebb49a4e783dabc8d5b26..eb7a4f115d666b80d66cdaba402118a6aaa73113 100644
--- a/ui/ozone/platform/dri/hardware_display_controller.h
+++ b/ui/ozone/platform/dri/hardware_display_controller.h
@@ -125,6 +125,9 @@ class OZONE_EXPORT HardwareDisplayController
   // Returns true if the page flip was successfully registered, false otherwise.
   bool SchedulePageFlip(const base::Closure& callback);
 
+  // Like |SchedulePageFlip| but synchronous.
+  bool PageFlip();
+
   // Set the hardware cursor to show the contents of |surface|.
   bool SetCursor(const scoped_refptr<ScanoutBuffer>& buffer);
 
@@ -158,7 +161,7 @@ class OZONE_EXPORT HardwareDisplayController
   // Returns true if any of the CRTCs is waiting for a page flip.
   bool HasPendingPageFlips() const;
 
-  bool ActualSchedulePageFlip();
+  bool ActualSchedulePageFlip(bool is_sync);
 
   void ProcessPageFlipRequest();