Update from https://crrev.com/320931

cc/base/swap_promise_monitor.h

-// Copyright 2013 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 CC_BASE_SWAP_PROMISE_MONITOR_H_
-#define CC_BASE_SWAP_PROMISE_MONITOR_H_
-
-#include "cc/base/cc_export.h"
-
-namespace cc {
-
-class LayerTreeHost;
-class LayerTreeHostImpl;
-
-// A SwapPromiseMonitor is used to monitor compositor state change that
-// should be associated with a SwapPromise, e.g. SetNeedsCommit() is
-// called on main thread or SetNeedsRedraw() is called on impl thread.
-// Creating a SwapPromiseMonitor will insert itself into a LayerTreeHost
-// or LayerTreeHostImpl. You must provide a pointer to the appropriate
-// structure to the monitor (and only one of the two). Notification of
-// compositor state change will be sent through OnSetNeedsCommitOnMain()
-// or OnSetNeedsRedrawOnImpl(). When SwapPromiseMonitor is destroyed, it
-// will unregister itself from LayerTreeHost or LayerTreeHostImpl.
-class CC_EXPORT SwapPromiseMonitor {
- public:
-  // If the monitor lives on the main thread, pass in layer_tree_host
-  // and set layer_tree_host_impl to nullptr.
-  // If the monitor lives on the impl thread, pass in layer_tree_host_impl
-  // and set layer_tree_host to nullptr.
-  SwapPromiseMonitor(LayerTreeHost* layer_tree_host,
-                     LayerTreeHostImpl* layer_tree_host_impl);
-  virtual ~SwapPromiseMonitor();
-
-  virtual void OnSetNeedsCommitOnMain() = 0;
-  virtual void OnSetNeedsRedrawOnImpl() = 0;
-  virtual void OnForwardScrollUpdateToMainThreadOnImpl() = 0;
-
- protected:
-  LayerTreeHost* layer_tree_host_;
-  LayerTreeHostImpl* layer_tree_host_impl_;
-};
-
-}  // namespace cc
-
-#endif  // CC_BASE_SWAP_PROMISE_MONITOR_H_