Add LoadState reporting to the mojo proxy resolver.

net/base/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_BASE_LOAD_STATE_CHANGE_COALESCER_H_

[eroman, 2015/03/06 05:13:01]

please move this into the net/proxy directory. This is very specific to the mojo
proxy resolver, I can't imagine any other code using this functionality.

[Sam McNally, 2015/03/06 09:33:02]

Done.

+#define NET_BASE_LOAD_STATE_CHANGE_COALESCER_H_
+
+#include "base/cancelable_callback.h"
+#include "base/time/time.h"
+#include "net/base/load_states.h"
+#include "net/base/net_export.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

[eroman, 2015/03/06 05:13:01]

"LoadState is discarded"

[Sam McNally, 2015/03/06 09:33:02]

Done.

+// 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 NET_EXPORT_PRIVATE 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::CancelableClosure pending_load_state_change_;
+  LoadState committed_load_state_;
+  LoadState pending_load_state_;
+
+  DISALLOW_COPY_AND_ASSIGN(LoadStateChangeCoalescer);
+};
+
+}  // namespace net
+
+#endif  // NET_BASE_LOAD_STATE_CHANGE_COALESCER_H_