Convert video capture pipline to base::TimeTicks

content/browser/renderer_host/media/video_capture_oracle.h

 // Copyright (c) 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 CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_ORACLE_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_ORACLE_H_
 
 #include "base/callback_forward.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
 #include "content/common/content_export.h"
 
 namespace content {
 
 // Filters a sequence of events to achieve a target frequency.
 class CONTENT_EXPORT SmoothEventSampler {
  public:
   explicit SmoothEventSampler(base::TimeDelta capture_period,
                               bool events_are_reliable,
                               int redundant_capture_goal);
 
   // Add a new event to the event history, and return whether it ought to be
   // sampled based on the desired |capture_period|. The event is not recorded as
   // a sample until RecordSample() is called.
-  bool AddEventAndConsiderSampling(base::Time event_time);
+  bool AddEventAndConsiderSampling(base::TimeTicks event_time);
 
   // Operates on the last event added by AddEventAndConsiderSampling(), marking
   // it as sampled. After this point we are current in the stream of events, as
   // we have sampled the most recent event.
   void RecordSample();
 
   // Returns true if, at time |event_time|, sampling should occur because too
   // much time will have passed relative to the last event and/or sample.
-  bool IsOverdueForSamplingAt(base::Time event_time) const;
+  bool IsOverdueForSamplingAt(base::TimeTicks event_time) const;
 
   // Returns true if AddEventAndConsiderSampling() has been called since the
   // last call to RecordSample().
   bool HasUnrecordedEvent() const;
 
  private:
   const bool events_are_reliable_;
   const base::TimeDelta capture_period_;
   const int redundant_capture_goal_;
   const base::TimeDelta token_bucket_capacity_;
 
-  base::Time current_event_;
-  base::Time last_sample_;
+  base::TimeTicks current_event_;
+  base::TimeTicks last_sample_;
   int overdue_sample_count_;
   base::TimeDelta token_bucket_;
 
   DISALLOW_COPY_AND_ASSIGN(SmoothEventSampler);
 };
 
 // VideoCaptureOracle manages the producer-side throttling of captured frames
 // from a video capture device.  It is informed of every update by the device;
 // this empowers it to look into the future and decide if a particular frame
 // ought to be captured in order to achieve its target frame rate.
 class CONTENT_EXPORT VideoCaptureOracle {
  public:
   enum Event {
     kTimerPoll,
     kCompositorUpdate,
     kSoftwarePaint,
   };
 
   VideoCaptureOracle(base::TimeDelta capture_period,
                      bool events_are_reliable);
   virtual ~VideoCaptureOracle() {}
 
   // Record an event of type |event|, and decide whether the caller should do a
   // frame capture immediately. Decisions of the oracle are final: the caller
   // must do what it is told.
-  bool ObserveEventAndDecideCapture(
-      Event event,
-      base::Time event_time);
+  bool ObserveEventAndDecideCapture(Event event, base::TimeTicks event_time);
 
   // Record the start of a capture.  Returns a frame_number to be used with
   // CompleteCapture().
   int RecordCapture();
 
   // Record the completion of a capture.  Returns true iff the captured frame
   // should be delivered.
-  bool CompleteCapture(int frame_number, base::Time timestamp);
+  bool CompleteCapture(int frame_number, base::TimeTicks timestamp);
 
   base::TimeDelta capture_period() const { return capture_period_; }
 
  private:
 
   // Time between frames.
   const base::TimeDelta capture_period_;
 
   // Incremented every time a paint or update event occurs.
   int frame_number_;
 
   // Stores the frame number from the last delivered frame.
   int last_delivered_frame_number_;
 
   // Stores the timestamp of the last delivered frame.
-  base::Time last_delivered_frame_timestamp_;
+  base::TimeTicks last_delivered_frame_timestamp_;
 
   // Tracks present/paint history.
   SmoothEventSampler sampler_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_ORACLE_H_