CC should use TimeTicks and TimeDelta to represent time

cc/animation/animation.h

Index: cc/animation/animation.h
diff --git a/cc/animation/animation.h b/cc/animation/animation.h
index f996c38bbb3dd410bad69189955c8533a2b77e00..893141147ca0de36a4d938d808a8e3daf1c48078 100644
--- a/cc/animation/animation.h
+++ b/cc/animation/animation.h
@@ -7,6 +7,7 @@
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
 #include "cc/base/cc_export.h"
 
 namespace cc {
@@ -60,7 +61,7 @@ class CC_EXPORT Animation {
   TargetProperty target_property() const { return target_property_; }
 
   RunState run_state() const { return run_state_; }
-  void SetRunState(RunState run_state, double monotonic_time);
+  void SetRunState(RunState run_state, base::TimeTicks monotonic_time);
 
   // This is the number of times that the animation will play. If this
   // value is zero the animation will not play. If it is negative, then
@@ -68,15 +69,25 @@ class CC_EXPORT Animation {
   int iterations() const { return iterations_; }
   void set_iterations(int n) { iterations_ = n; }
 
-  double start_time() const { return start_time_; }
-  void set_start_time(double monotonic_time) { start_time_ = monotonic_time; }
-  bool has_set_start_time() const { return !!start_time_; }
+  double start_time() const {

[ajuma, 2014/04/08 15:44:16]

We should make this return a TimeTicks instead of a double.

+    return (start_time_ - base::TimeTicks()).InSecondsF();
+  }
+  void set_start_time(base::TimeTicks monotonic_time) {
+    start_time_ = monotonic_time;
+  }
+  bool has_set_start_time() const {
+    return !!(start_time_ - base::TimeTicks()).InSecondsF();

[ajuma, 2014/04/08 15:44:16]

return start_time_ != base::TimeTicks()

+  }
 
-  double time_offset() const { return time_offset_; }
-  void set_time_offset(double monotonic_time) { time_offset_ = monotonic_time; }
+  double time_offset() const {
+    return (time_offset_ - base::TimeTicks()).InSecondsF();

[ajuma, 2014/04/08 15:44:16]

It seems like time_offset_ should be a TimeDelta, and this function should
return a TimeDelta too.

+  }
+  void set_time_offset(base::TimeTicks monotonic_time) {

[ajuma, 2014/04/08 15:44:16]

TimeDelta?

+    time_offset_ = monotonic_time;
+  }
 
-  void Suspend(double monotonic_time);
-  void Resume(double monotonic_time);
+  void Suspend(base::TimeTicks monotonic_time);
+  void Resume(base::TimeTicks monotonic_time);
 
   // If alternates_direction is true, on odd numbered iterations we reverse the
   // curve.
@@ -85,7 +96,7 @@ class CC_EXPORT Animation {
     alternates_direction_ = alternates;
   }
 
-  bool IsFinishedAt(double monotonic_time) const;
+  bool IsFinishedAt(base::TimeTicks monotonic_time) const;
   bool is_finished() const {
     return run_state_ == Finished ||
         run_state_ == Aborted ||
@@ -116,11 +127,11 @@ class CC_EXPORT Animation {
 
   // Takes the given absolute time, and using the start time and the number
   // of iterations, returns the relative time in the current iteration.
-  double TrimTimeToCurrentIteration(double monotonic_time) const;
+  double TrimTimeToCurrentIteration(base::TimeTicks monotonic_time) const;
 
   scoped_ptr<Animation> Clone() const;
   scoped_ptr<Animation> CloneAndInitialize(RunState initial_run_state,
-                                           double start_time) const;
+                                           base::TimeTicks start_time) const;
   bool is_controlling_instance() const { return is_controlling_instance_; }
 
   void PushPropertiesTo(Animation* other) const;
@@ -149,14 +160,14 @@ class CC_EXPORT Animation {
   TargetProperty target_property_;
   RunState run_state_;
   int iterations_;
-  double start_time_;
+  base::TimeTicks start_time_;
   bool alternates_direction_;
 
   // The time offset effectively pushes the start of the animation back in time.
   // This is used for resuming paused animations -- an animation is added with a
   // non-zero time offset, causing the animation to skip ahead to the desired
   // point in time.
-  double time_offset_;
+  base::TimeTicks time_offset_;

[ajuma, 2014/04/08 15:44:16]

TimeDelta seems more appropriate for an offset.

 
   bool needs_synchronized_start_time_;
   bool received_finished_event_;