Split ProxyResolverV8Tracing into an implementation and a wrapper.

net/proxy/load_state_change_coalescer.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 NET_PROXY_LOAD_STATE_CHANGE_COALESCER_H_
-#define NET_PROXY_LOAD_STATE_CHANGE_COALESCER_H_
-
-#include "base/cancelable_callback.h"
-#include "base/time/time.h"
-#include "base/timer/timer.h"
-#include "net/base/load_states.h"
-
-namespace net {
-
-// A class that coalesces LoadState changes. When a new LoadState is reported,
-// it becomes the pending LoadState and is queued for |timeout|. If the timeout
-// elapses without another new LoadState, the pending LoadState becomes the
-// committed LoadState and the callback is called with that LoadState. If a new
-// LoadState is reported before the timeout has elapsed, the pending LoadState
-// is discarded and the new LoadState becomes the new pending LoadState, unless
-// it's the same as the committed LoadState, in which case no pending LoadState
-// is queued.
-class LoadStateChangeCoalescer {
- public:
-  LoadStateChangeCoalescer(const base::Callback<void(LoadState)>& callback,
-                           const base::TimeDelta& timeout,
-                           LoadState initial_load_state);
-  ~LoadStateChangeCoalescer();
-
-  // Adds a LoadState change to the pipeline. If it isn't coalesced, |callback_|
-  // will be called with |load_state| after |timeout_|.
-  void LoadStateChanged(LoadState load_state);
-
- private:
-  void SendLoadStateChanged();
-
-  // The callback to call to report a LoadState change.
-  const base::Callback<void(LoadState)> callback_;
-
-  // The amount of time for which a LoadState change can be coalesced.
-  const base::TimeDelta timeout_;
-
-  base::OneShotTimer<LoadStateChangeCoalescer> timer_;
-  LoadState committed_load_state_;
-  LoadState pending_load_state_;
-
-  DISALLOW_COPY_AND_ASSIGN(LoadStateChangeCoalescer);
-};
-
-}  // namespace net
-
-#endif  // NET_PROXY_LOAD_STATE_CHANGE_COALESCER_H_