cc: Misc animation refactoring

cc/test/layer_tree_test.cc

Index: cc/test/layer_tree_test.cc
diff --git a/cc/test/layer_tree_test.cc b/cc/test/layer_tree_test.cc
index 129a27d82b01edf46ee104248ddef8dca111dcdf..9690362009b7cad80035b68c0e02b1e93a466d60 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -349,10 +349,9 @@ class LayerTreeHostImplForTesting : public LayerTreeHostImpl {
   void UpdateAnimationState(bool start_ready_animations) override {
     LayerTreeHostImpl::UpdateAnimationState(start_ready_animations);
     bool has_unfinished_animation = false;
-    AnimationRegistrar::AnimationControllerMap::const_iterator iter =
-        active_animation_controllers().begin();
-    for (; iter != active_animation_controllers().end(); ++iter) {
-      if (iter->second->HasActiveAnimation()) {
+    for (const auto& it :
+         animation_registrar()->active_animation_controllers()) {
+      if (it.second->HasActiveAnimation()) {
         has_unfinished_animation = true;
         break;
       }