Re-land r136486 (reverted in r136500).

media/base/download_rate_monitor.h

Index: media/base/download_rate_monitor.h
diff --git a/media/base/download_rate_monitor.h b/media/base/download_rate_monitor.h
deleted file mode 100644
index 4fca328858e1f8c187e53728ed1aed0338b332be..0000000000000000000000000000000000000000
--- a/media/base/download_rate_monitor.h
+++ /dev/null
@@ -1,157 +0,0 @@
-// Copyright (c) 2011 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 MEDIA_BASE_DOWNLOAD_RATE_MONITOR_H_
-#define MEDIA_BASE_DOWNLOAD_RATE_MONITOR_H_
-
-#include <deque>
-
-#include "base/callback.h"
-#include "base/time.h"
-#include "media/base/media_export.h"
-
-namespace media {
-
-// Measures download speed based on the rate at which a media file is buffering.
-// Signals when it believes the media file can be played back without needing to
-// pause to buffer.
-class MEDIA_EXPORT DownloadRateMonitor {
- public:
-  DownloadRateMonitor();
-  ~DownloadRateMonitor();
-
-  // Begin measuring download rate. The monitor will run |canplaythrough_cb|
-  // when it believes the media can be played back without needing to pause to
-  // buffer. |media_bitrate| is the bitrate of the video.
-  void Start(const base::Closure& canplaythrough_cb, int media_bitrate,
-             bool streaming, bool local_source);
-
-  // Notifies the monitor of the current number of bytes buffered by the media
-  // file at what timestamp. The monitor expects subsequent calls to
-  // SetBufferedBytes to have monotonically nondecreasing timestamps.
-  // Calls to the method are ignored if monitor has not been started or is
-  // stopped.
-  void SetBufferedBytes(int64 buffered_bytes, const base::Time& timestamp);
-
-  // Notifies the monitor when the media file has paused or continued
-  // downloading data.
-  void SetNetworkActivity(bool is_downloading_data);
-
-  void set_total_bytes(int64 total_bytes) { total_bytes_ = total_bytes; }
-
-  // Stop monitoring download rate. This does not discard previously learned
-  // information, but it will no longer factor incoming information into its
-  // canplaythrough estimation.
-  void Stop();
-
-  // Resets monitor to uninitialized state.
-  void Reset();
-
- private:
-  // Represents a point in time in which the media was buffering data.
-  struct BufferingPoint {
-    // The number of bytes buffered by the media player at |timestamp|.
-    int64 buffered_bytes;
-    // Time at which buffering measurement was taken.
-    base::Time timestamp;
-  };
-
-  // Represents a span of time in which the media was buffering data.
-  class Sample {
-   public:
-    Sample();
-    Sample(const BufferingPoint& start, const BufferingPoint& end);
-    ~Sample();
-
-    // Set the end point of the data sample.
-    void set_end(const BufferingPoint& new_end);
-
-    const BufferingPoint& start() const { return start_; }
-    const BufferingPoint& end() const { return end_; }
-
-    // Returns the bytes downloaded per second in this sample. Returns -1.0 if
-    // sample is invalid.
-    float bytes_per_second() const;
-
-    // Returns the seconds elapsed in this sample. Returns -1.0 if the sample
-    // has not begun yet.
-    float seconds_elapsed() const;
-
-    // Returns bytes downloaded in this sample. Returns -1.0 if the sample has
-    // not begun yet.
-    int64 bytes_downloaded() const;
-
-    // Returns true if Sample has not been initialized.
-    bool is_null() const;
-
-    // Resets the sample to an uninitialized state.
-    void Reset();
-
-    // Restarts the sample to begin its measurement at what was previously its
-    // end point.
-    void RestartAtEndBufferingPoint();
-
-   private:
-    BufferingPoint start_;
-    BufferingPoint end_;
-  };
-
-  int64 bytes_downloaded_in_window() const;
-  float seconds_elapsed_in_window() const;
-
-  // Updates window with latest sample if it is ready.
-  void UpdateSampleWindow();
-
-  // Returns an approximation of the current download rate in bytes per second.
-  // Returns -1.0 if unknown.
-  float ApproximateDownloadByteRate() const;
-
-  // Helper method that returns true if the monitor believes it should fire the
-  // |canplaythrough_cb_|.
-  bool ShouldNotifyCanPlayThrough();
-
-  // Examines the download rate and fires the |canplaythrough_cb_| callback if
-  // the monitor deems it the right time.
-  void NotifyCanPlayThroughIfNeeded();
-
-  // Callback to run when the monitor believes the media can play through
-  // without needing to pause to buffer.
-  base::Closure canplaythrough_cb_;
-
-  // Indicates whether the monitor has run the |canplaythrough_cb_|.
-  bool has_notified_can_play_through_;
-
-  // Measurements used to approximate download speed.
-  Sample current_sample_;
-  std::deque<Sample> sample_window_;
-
-  // True if actively downloading bytes, false otherwise.
-  bool is_downloading_data_;
-
-  // Total number of bytes in the media file, 0 if unknown or undefined.
-  int64 total_bytes_;
-
-  // Amount of bytes buffered.
-  int64 buffered_bytes_;
-
-  // True if the media file is from a local source, e.g. file:// protocol or a
-  // webcam stream.
-  bool local_source_;
-
-  // Bitrate of the media file, 0 if unknown.
-  int bitrate_;
-
-  // True if the monitor has not yet started or has been stopped, false
-  // otherwise.
-  bool stopped_;
-
-  // True if the data source is a streaming source, false otherwise.
-  bool streaming_;
-
-  DISALLOW_COPY_AND_ASSIGN(DownloadRateMonitor);
-};
-
-}  // namespace media
-
-#endif  // MEDIA_BASE_DOWNLOAD_RATE_MONITOR_H_