Make Keyframe use TimeTicks/TimeDelta to represent time instead of double.

cc/animation/layer_animation_controller.cc

Index: cc/animation/layer_animation_controller.cc
diff --git a/cc/animation/layer_animation_controller.cc b/cc/animation/layer_animation_controller.cc
index f621ad318c4d5470442b842be7fee9ab4eee0333..c9d81cf0e9d29249993b44f26846aaec709b5f3e 100644
--- a/cc/animation/layer_animation_controller.cc
+++ b/cc/animation/layer_animation_controller.cc
@@ -148,8 +148,8 @@ void LayerAnimationController::AccumulatePropertyUpdates(
     if (!animation->InEffect(monotonic_time))
       continue;
 
-    double trimmed =
-        animation->TrimTimeToCurrentIteration(monotonic_time).InSecondsF();
+    base::TimeDelta trimmed =
+        animation->TrimTimeToCurrentIteration(monotonic_time);
     switch (animation->target_property()) {
       case Animation::Opacity: {
         AnimationEvent event(AnimationEvent::PropertyUpdate,
@@ -861,9 +861,8 @@ void LayerAnimationController::TickAnimations(base::TimeTicks monotonic_time) {
       if (!animations_[i]->InEffect(monotonic_time))
         continue;
 
-      double trimmed = animations_[i]
-                           ->TrimTimeToCurrentIteration(monotonic_time)
-                           .InSecondsF();
+      base::TimeDelta trimmed =
+          animations_[i]->TrimTimeToCurrentIteration(monotonic_time);
 
       switch (animations_[i]->target_property()) {
         case Animation::Transform: {