Remove return bool in SurfaceOzoneEGL::OnSwapBuffersAsync

ui/ozone/platform/cast/surface_ozone_egl_cast.h

 // 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.
 
 #ifndef UI_OZONE_PLATFORM_CAST_SURFACE_OZONE_EGL_CAST_H_
 #define UI_OZONE_PLATFORM_CAST_SURFACE_OZONE_EGL_CAST_H_
 
 #include "ui/ozone/public/surface_ozone_egl.h"
 
 namespace ui {
 
 class SurfaceFactoryCast;
 
 // EGL surface wrapper for OzonePlatformCast.
 class SurfaceOzoneEglCast : public SurfaceOzoneEGL {
  public:
   explicit SurfaceOzoneEglCast(SurfaceFactoryCast* parent) : parent_(parent) {}
   ~SurfaceOzoneEglCast() override;
 
   // SurfaceOzoneEGL implementation:
   intptr_t GetNativeWindow() override;
   bool OnSwapBuffers() override;
-  bool OnSwapBuffersAsync(const SwapCompletionCallback& callback) override;
+  void OnSwapBuffersAsync(const SwapCompletionCallback& callback) override;
   bool ResizeNativeWindow(const gfx::Size& viewport_size) override;
   scoped_ptr<gfx::VSyncProvider> CreateVSyncProvider() override;
 
  private:
   SurfaceFactoryCast* parent_;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceOzoneEglCast);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_CAST_SURFACE_OZONE_EGL_CAST_H_