[Ozone-DRI] Listen for swap events

ui/ozone/platform/dri/gbm_surfaceless.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/ozone/platform/dri/gbm_surfaceless.h"
 
 #include "ui/ozone/platform/dri/dri_vsync_provider.h"
 #include "ui/ozone/platform/dri/dri_window_delegate.h"
 #include "ui/ozone/platform/dri/gbm_buffer.h"
 #include "ui/ozone/platform/dri/hardware_display_controller.h"
@@ skipping 10 matching lines @@
   NOTREACHED();
   return 0;
 }
 
 bool GbmSurfaceless::ResizeNativeWindow(const gfx::Size& viewport_size) {
   NOTIMPLEMENTED();
   return false;
 }
 
 bool GbmSurfaceless::OnSwapBuffers() {
-  HardwareDisplayController* controller = window_delegate_->GetController();
-  if (!controller)
-    return true;
-
-  bool success = controller->SchedulePageFlip();
-  controller->WaitForPageFlipEvent();
-
-  return success;
+  NOTREACHED();
+  return false;
 }
 
 bool GbmSurfaceless::OnSwapBuffersAsync(
     const SwapCompletionCallback& callback) {
-  bool success = OnSwapBuffers();
-  callback.Run();
-  return success;
+  HardwareDisplayController* controller = window_delegate_->GetController();
+  if (!controller) {
+    callback.Run();
+    return true;
+  }
+
+  return controller->SchedulePageFlip(callback);
 }
 
 scoped_ptr<gfx::VSyncProvider> GbmSurfaceless::CreateVSyncProvider() {
   return scoped_ptr<gfx::VSyncProvider>(new DriVSyncProvider(window_delegate_));
 }
 
 }  // namespace ui