Do glFinish before sending snapshot latency info to browser

gpu/ipc/service/child_window_surface_win.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 "gpu/ipc/service/child_window_surface_win.h"
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/memory/ptr_util.h"
@@ skipping 147 matching lines @@
 gfx::SwapResult ChildWindowSurfaceWin::PostSubBuffer(int x,
                                                      int y,
                                                      int width,
                                                      int height) {
   gfx::SwapResult result =
       NativeViewGLSurfaceEGL::PostSubBuffer(x, y, width, height);
   child_window_.ClearInvalidContents();
   return result;
 }
 
+void ChildWindowSurfaceWin::WaitForSnapshotRendering() {
+  DCHECK(gl::GLContext::GetCurrent()->IsCurrent(this));
+  glFinish();
+}
+
 ChildWindowSurfaceWin::~ChildWindowSurfaceWin() {
 }
 
 }  // namespace gpu