Do glFinish before sending snapshot latency info to browser

gpu/ipc/service/child_window_surface_win.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 GPU_IPC_SERVICE_CHILD_WINDOW_SURFACE_WIN_H_
 #define GPU_IPC_SERVICE_CHILD_WINDOW_SURFACE_WIN_H_
 
 #include "base/memory/weak_ptr.h"
 #include "gpu/ipc/service/child_window_win.h"
 #include "gpu/ipc/service/image_transport_surface_delegate.h"
@@ skipping 10 matching lines @@
                         HWND parent_window);
 
   // GLSurface implementation.
   EGLConfig GetConfig() override;
   bool Resize(const gfx::Size& size,
               float scale_factor,
               bool has_alpha) override;
   bool InitializeNativeWindow() override;
   gfx::SwapResult SwapBuffers() override;
   gfx::SwapResult PostSubBuffer(int x, int y, int width, int height) override;
+  void WaitForSnapshotRendering() override;
 
  protected:
   ~ChildWindowSurfaceWin() override;
 
  private:
   ChildWindowWin child_window_;
   bool alpha_;
   bool first_swap_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildWindowSurfaceWin);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_IPC_SERVICE_CHILD_WINDOW_SURFACE_WIN_H_