Update from https://crrev.com/315085

ui/gl/gl_context.cc

 // Copyright (c) 2012 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 <string>
 
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/threading/thread_local.h"
@@ skipping 20 matching lines @@
 GLContext::ScopedReleaseCurrent::~ScopedReleaseCurrent() {
   if (!canceled_ && GetCurrent()) {
     GetCurrent()->ReleaseCurrent(NULL);
   }
 }
 
 void GLContext::ScopedReleaseCurrent::Cancel() {
   canceled_ = true;
 }
 
-GLContext::FlushEvent::FlushEvent() {
-}
-
-GLContext::FlushEvent::~FlushEvent() {
-}
-
-void GLContext::FlushEvent::Signal() {
-  flag_.Set();
-}
-
-bool GLContext::FlushEvent::IsSignaled() {
-  return flag_.IsSet();
-}
-
 GLContext::GLContext(GLShareGroup* share_group) :
     share_group_(share_group),
     swap_interval_(1),
     force_swap_interval_zero_(false) {
   if (!share_group_.get())
     share_group_ = new GLShareGroup;
 
   share_group_->AddContext(this);
 }
 
 GLContext::~GLContext() {
   share_group_->RemoveContext(this);
   if (GetCurrent() == this) {
     SetCurrent(NULL);
   }
 }
 
-scoped_refptr<GLContext::FlushEvent> GLContext::SignalFlush() {
-  DCHECK(IsCurrent(NULL));
-  scoped_refptr<FlushEvent> flush_event = new FlushEvent();
-  flush_events_.push_back(flush_event);
-  return flush_event;
-}
-
 bool GLContext::GetTotalGpuMemory(size_t* bytes) {
   DCHECK(bytes);
   *bytes = 0;
   return false;
 }
 
 void GLContext::SetSafeToForceGpuSwitch() {
 }
 
 bool GLContext::ForceGpuSwitchIfNeeded() {
@@ skipping 134 matching lines @@
 
 void GLContext::OnReleaseVirtuallyCurrent(GLContext* virtual_context) {
   if (virtual_gl_api_)
     virtual_gl_api_->OnReleaseVirtuallyCurrent(virtual_context);
 }
 
 void GLContext::SetRealGLApi() {
   SetGLToRealGLApi();
 }
 
-void GLContext::OnFlush() {
-  for (size_t n = 0; n < flush_events_.size(); n++)
-    flush_events_[n]->Signal();
-  flush_events_.clear();
-}
-
 GLContextReal::GLContextReal(GLShareGroup* share_group)
     : GLContext(share_group) {}
 
 GLContextReal::~GLContextReal() {}
 
 void GLContextReal::SetCurrent(GLSurface* surface) {
   GLContext::SetCurrent(surface);
   current_real_context_.Pointer()->Set(surface ? this : NULL);
 }
 
 }  // namespace gfx