CC Animation: Start replacing int layer_id with ElementId element_id.

cc/animation/animation_events.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/animation/animation_events.h"
 
 namespace cc {
 
 AnimationEvent::AnimationEvent(AnimationEvent::Type type,
-                               int layer_id,
+                               ElementId element_id,
                                int group_id,
                                TargetProperty::Type target_property,
                                base::TimeTicks monotonic_time)
     : type(type),
-      layer_id(layer_id),
+      element_id(element_id),
       group_id(group_id),
       target_property(target_property),
       monotonic_time(monotonic_time),
       is_impl_only(false),
       opacity(0.f) {}
 
 AnimationEvent::AnimationEvent(const AnimationEvent& other) {
   type = other.type;
-  layer_id = other.layer_id;
+  element_id = other.element_id;
   group_id = other.group_id;
   target_property = other.target_property;
   monotonic_time = other.monotonic_time;
   is_impl_only = other.is_impl_only;
   opacity = other.opacity;
   transform = other.transform;
   filters = other.filters;
   animation_start_time = other.animation_start_time;
   if (other.curve)
     curve = other.curve->Clone();
 }
 
 AnimationEvent& AnimationEvent::operator=(const AnimationEvent& other) {
   type = other.type;
-  layer_id = other.layer_id;
+  element_id = other.element_id;
   group_id = other.group_id;
   target_property = other.target_property;
   monotonic_time = other.monotonic_time;
   is_impl_only = other.is_impl_only;
   opacity = other.opacity;
   transform = other.transform;
   filters = other.filters;
   animation_start_time = other.animation_start_time;
   if (other.curve)
     curve = other.curve->Clone();
   return *this;
 }
 
 AnimationEvent::~AnimationEvent() {}
 
 AnimationEvents::AnimationEvents() {}
 
 AnimationEvents::~AnimationEvents() {}
 
 }  // namespace cc