Change cc::ElementId to be a uint64_t

cc/animation/animation_host.h

Index: cc/animation/animation_host.h
diff --git a/cc/animation/animation_host.h b/cc/animation/animation_host.h
index 5e4f8e077cb051533a52f7790e0126acff70150a..82e8628bc0607f4da267e031eac79b64921a3ee7 100644
--- a/cc/animation/animation_host.h
+++ b/cc/animation/animation_host.h
@@ -47,9 +47,7 @@ class CC_ANIMATION_EXPORT AnimationHost
     : public NON_EXPORTED_BASE(MutatorHost) {
  public:
   using ElementToAnimationsMap =
-      std::unordered_map<ElementId,
-                         scoped_refptr<ElementAnimations>,
-                         ElementIdHash>;
+      std::unordered_map<ElementId, scoped_refptr<ElementAnimations>>;
   using PlayersList = std::vector<scoped_refptr<AnimationPlayer>>;
 
   static std::unique_ptr<AnimationHost> CreateMainInstance();