Replace erroneous use of base::Time with base::TimeTicks throughout media code.

media/base/clock.h

Index: media/base/clock.h
diff --git a/media/base/clock.h b/media/base/clock.h
index 267666f668aeefc63682b7dcd4fc0e24ec7d2d14..6a86106c17781a38733f9c6585b67276909582c6 100644
--- a/media/base/clock.h
+++ b/media/base/clock.h
@@ -10,16 +10,16 @@
 #include "media/base/media_export.h"
 
 namespace base {
-class Clock;
+class TickClock;
 }  // namespace base
 
 namespace media {
 
 // A clock represents a single source of time to allow audio and video streams
 // to synchronize with each other.  Clock essentially tracks the media time with
-// respect to some other source of time, whether that may be the system clock or
-// updates via SetTime(). Clock uses linear interpolation to calculate the
-// current media time since the last time SetTime() was called.
+// respect to some other source of time, whether that may be the monotonic
+// system clock or updates via SetTime(). Clock uses linear interpolation to
+// calculate the current media time since the last time SetTime() was called.
 //
 // Clocks start off paused with a playback rate of 1.0f and a media time of 0.
 //
@@ -28,9 +28,12 @@ namespace media {
 // TODO(scherkus): Clock will some day be responsible for executing callbacks
 // given a media time.  This will be used primarily by video renderers.  For now
 // we'll keep using a poll-and-sleep solution.
+//
+// TODO(miu): Rename media::Clock to avoid confusion (and tripping up the media
+// PRESUBMIT script on future changes).
 class MEDIA_EXPORT Clock {
  public:
-  explicit Clock(base::Clock* clock);
+  explicit Clock(base::TickClock* clock);
   ~Clock();
 
   // Returns true if the clock is running.
@@ -88,13 +91,13 @@ class MEDIA_EXPORT Clock {
   // the |max_time_| cap.
   base::TimeDelta EstimatedElapsedTime();
 
-  // Returns the current media time treating the given time as the latest
-  // value as returned by |time_provider_|.
-  base::TimeDelta ElapsedViaProvidedTime(const base::Time& time) const;
+  // Translates |time| into the current media time, based on the perspective of
+  // the monotonically-increasing system clock.
+  base::TimeDelta ElapsedViaProvidedTime(const base::TimeTicks& time) const;
 
   base::TimeDelta ClampToValidTimeRange(base::TimeDelta time) const;
 
-  base::Clock* const clock_;
+  base::TickClock* const clock_;
 
   // Whether the clock is running.
   bool playing_;
@@ -103,9 +106,9 @@ class MEDIA_EXPORT Clock {
   // allowed.
   bool underflow_;
 
-  // The system clock time when this clock last starting playing or had its
-  // time set via SetTime().
-  base::Time reference_;
+  // The monotonic system clock time when this Clock last started playing or had
+  // its time set via SetTime().
+  base::TimeTicks reference_;
 
   // Current accumulated amount of media time.  The remaining portion must be
   // calculated by comparing the system time to the reference time.