Remove return bool in SurfaceOzoneEGL::OnSwapBuffersAsync

ui/ozone/platform/cast/surface_ozone_egl_cast.cc

 // Copyright 2015 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/cast/surface_ozone_egl_cast.h"
 
 #include "ui/gfx/vsync_provider.h"
 #include "ui/ozone/platform/cast/surface_factory_cast.h"
 
 namespace ui {
 
 SurfaceOzoneEglCast::~SurfaceOzoneEglCast() {
   parent_->ChildDestroyed();
 }
 
 intptr_t SurfaceOzoneEglCast::GetNativeWindow() {
   return reinterpret_cast<intptr_t>(parent_->GetNativeWindow());
 }
 
 bool SurfaceOzoneEglCast::OnSwapBuffers() {
   return true;
 }
 
-bool SurfaceOzoneEglCast::OnSwapBuffersAsync(
+void SurfaceOzoneEglCast::OnSwapBuffersAsync(
     const SwapCompletionCallback& callback) {
   callback.Run(gfx::SwapResult::SWAP_ACK);
-  return true;
 }
 
 bool SurfaceOzoneEglCast::ResizeNativeWindow(const gfx::Size& viewport_size) {
   return parent_->ResizeDisplay(viewport_size);
 }
 
 scoped_ptr<gfx::VSyncProvider> SurfaceOzoneEglCast::CreateVSyncProvider() {
   return nullptr;
 }
 
 }  // namespace ui