Change cc::ElementId to be a uint64_t

cc/trees/layer_tree_impl.h

Index: cc/trees/layer_tree_impl.h
diff --git a/cc/trees/layer_tree_impl.h b/cc/trees/layer_tree_impl.h
index 6f1783cc0fae84ec515966a7ab1c79121d999660..38264a1d7dc4cb7b7e48f16508c8896b8524cdbc 100644
--- a/cc/trees/layer_tree_impl.h
+++ b/cc/trees/layer_tree_impl.h
@@ -516,13 +516,12 @@ class CC_EXPORT LayerTreeImpl {
   // Set of layers that need to push properties.
   std::unordered_set<LayerImpl*> layers_that_should_push_properties_;
 
-  std::unordered_map<ElementId, int, ElementIdHash> element_layers_map_;
+  std::unordered_map<ElementId::Id, int> element_layers_map_;
 
-  std::unordered_map<ElementId, float, ElementIdHash>
-      element_id_to_opacity_animations_;
-  std::unordered_map<ElementId, gfx::Transform, ElementIdHash>
+  std::unordered_map<ElementId::Id, float> element_id_to_opacity_animations_;
+  std::unordered_map<ElementId::Id, gfx::Transform>
       element_id_to_transform_animations_;
-  std::unordered_map<ElementId, FilterOperations, ElementIdHash>
+  std::unordered_map<ElementId::Id, FilterOperations>
       element_id_to_filter_animations_;
 
   // Maps from clip layer ids to scroll layer ids.  Note that this only includes