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..55e755149f326f3c89e30766a5736522b783f567 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::Id, scoped_refptr<ElementAnimations>>;

[wkorman, 2017/05/08 18:23:24]

My personal preference given our shift to support pdr@ pitch re: type safety,
and balancing readability/maintenance, would be to not leak ElementId::Id
outside of the class itself and just use ElementId and add operators / hash
funcs if needed. But I am ok trying it this way if we'd like.

   using PlayersList = std::vector<scoped_refptr<AnimationPlayer>>;
 
   static std::unique_ptr<AnimationHost> CreateMainInstance();