Switch to double for time calculations using playback rate.

media/base/time_source.h

 // Copyright 2014 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_TIME_SOURCE_H_
 #define MEDIA_BASE_TIME_SOURCE_H_
 
 #include "base/time/time.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
 // A TimeSource is capable of providing the current media time.
 class MEDIA_EXPORT TimeSource {
  public:
   TimeSource() {}
   virtual ~TimeSource() {}
 
   // Signal the time source to start ticking. It is expected that values from
   // CurrentMediaTime() will start increasing.
   virtual void StartTicking() = 0;
 
   // Signal the time source to stop ticking. It is expected that values from
   // CurrentMediaTime() will remain constant.
   virtual void StopTicking() = 0;
 
   // Updates the current playback rate. It is expected that values from
   // CurrentMediaTime() will eventually reflect the new playback rate (e.g., the
   // media time will advance at half speed if the rate was set to 0.5f).
-  virtual void SetPlaybackRate(float playback_rate) = 0;
+  virtual void SetPlaybackRate(double playback_rate) = 0;
 
   // Sets the media time to start ticking from. Only valid to call while the
   // time source is not ticking.
   virtual void SetMediaTime(base::TimeDelta time) = 0;
 
   // Returns the current media timestamp relative to the timestamp set by
   // SetMediaTime().
   //
   // Values returned are intended for informational purposes, such as displaying
   // UI with the current minute and second count. While it is guaranteed values
   // will never go backwards, the frequency at which they update may be low.
   virtual base::TimeDelta CurrentMediaTime() = 0;
 
   // Converts a media timestamp into a wall clock time. If the media time is
   // stopped, returns a null TimeTicks.
   //
   // |media_time| values too far ahead of the current media time will return an
   // estimated value; as such, these values may go backwards in time slightly.
   //
   // |media_time| values behind the current media time may be significantly
   // incorrect if the playback rate has changed recently. The only guarantee is
   // that the returned time will be less than the current wall clock time.
   virtual base::TimeTicks GetWallClockTime(base::TimeDelta media_time) = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_TIME_SOURCE_H_