CC::Animations should use TimeTicks & TimeDelta to represent time

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index ee73abacb10d97dd3ca75f798175334698160c87..60f0d650e6622a8f87ec7291fe8aa03d01c0c03c 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -1139,15 +1139,13 @@ scoped_ptr<base::Value> LayerTreeHost::AsValue() const {
   return state.PassAs<base::Value>();
 }
 
-void LayerTreeHost::AnimateLayers(base::TimeTicks time) {
+void LayerTreeHost::AnimateLayers(base::TimeTicks monotonic_time) {
   if (!settings_.accelerated_animation_enabled ||
       animation_registrar_->active_animation_controllers().empty())
     return;
 
   TRACE_EVENT0("cc", "LayerTreeHost::AnimateLayers");
 
-  double monotonic_time = (time - base::TimeTicks()).InSecondsF();
-
   AnimationRegistrar::AnimationControllerMap copy =
       animation_registrar_->active_animation_controllers();
   for (AnimationRegistrar::AnimationControllerMap::iterator iter = copy.begin();