Remove return bool in SurfaceOzoneEGL::OnSwapBuffersAsync

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

 // 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.
 
 #ifndef UI_OZONE_PLATFORM_DRM_GPU_GBM_SURFACELESS_H_
 #define UI_OZONE_PLATFORM_DRM_GPU_GBM_SURFACELESS_H_
 
 #include <vector>
 
 #include "ui/gfx/native_widget_types.h"
@@ skipping 18 matching lines @@
   GbmSurfaceless(scoped_ptr<DrmWindowProxy> window,
                  GbmSurfaceFactory* surface_manager);
   ~GbmSurfaceless() override;
 
   void QueueOverlayPlane(const OverlayPlane& plane);
 
   // SurfaceOzoneEGL:
   intptr_t GetNativeWindow() override;
   bool ResizeNativeWindow(const gfx::Size& viewport_size) override;
   bool OnSwapBuffers() override;
-  bool OnSwapBuffersAsync(const SwapCompletionCallback& callback) override;
+  void OnSwapBuffersAsync(const SwapCompletionCallback& callback) override;
   scoped_ptr<gfx::VSyncProvider> CreateVSyncProvider() override;
   bool IsUniversalDisplayLinkDevice() override;
 
  protected:
   scoped_ptr<DrmWindowProxy> window_;
 
   GbmSurfaceFactory* surface_manager_;
 
   std::vector<OverlayPlane> planes_;
 
   DISALLOW_COPY_AND_ASSIGN(GbmSurfaceless);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_DRM_GPU_GBM_SURFACELESS_H_