Remove return bool in SurfaceOzoneEGL::OnSwapBuffersAsync

ui/ozone/platform/drm/gpu/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/drm/gpu/gbm_surfaceless.h"
 
 #include "ui/ozone/platform/drm/gpu/drm_device.h"
 #include "ui/ozone/platform/drm/gpu/drm_vsync_provider.h"
 #include "ui/ozone/platform/drm/gpu/drm_window_proxy.h"
 #include "ui/ozone/platform/drm/gpu/gbm_surface_factory.h"
@@ skipping 22 matching lines @@
 
 bool GbmSurfaceless::ResizeNativeWindow(const gfx::Size& viewport_size) {
   return true;
 }
 
 bool GbmSurfaceless::OnSwapBuffers() {
   NOTREACHED();
   return false;
 }
 
-bool GbmSurfaceless::OnSwapBuffersAsync(
+void GbmSurfaceless::OnSwapBuffersAsync(
     const SwapCompletionCallback& callback) {
   window_->SchedulePageFlip(planes_, callback);
   planes_.clear();
-  return true;
 }
 
 scoped_ptr<gfx::VSyncProvider> GbmSurfaceless::CreateVSyncProvider() {
   return make_scoped_ptr(new DrmVSyncProvider(window_.get()));
 }
 
 bool GbmSurfaceless::IsUniversalDisplayLinkDevice() {
   return planes_.empty() ? false : planes_[0].buffer->RequiresGlFinish();
 }
 
 }  // namespace ui