Change cc::ElementId to be a uint64_t

cc/animation/animation_host.cc

Index: cc/animation/animation_host.cc
diff --git a/cc/animation/animation_host.cc b/cc/animation/animation_host.cc
index 80dfae1670ca3cf9ee0622b6e01b73898ef42171..8c293db8694797628e3e01e05817195bae3c434a 100644
--- a/cc/animation/animation_host.cc
+++ b/cc/animation/animation_host.cc
@@ -129,7 +129,7 @@ void AnimationHost::RegisterPlayerForElement(ElementId element_id,
   if (!element_animations) {
     element_animations = ElementAnimations::Create();
     element_animations->SetElementId(element_id);
-    element_to_animations_map_[element_animations->element_id()] =
+    element_to_animations_map_[element_animations->element_id().id] =
         element_animations;
   }
 
@@ -153,7 +153,7 @@ void AnimationHost::UnregisterPlayerForElement(ElementId element_id,
 
   if (element_animations->IsEmpty()) {
     element_animations->ClearAffectedElementTypes();
-    element_to_animations_map_.erase(element_animations->element_id());
+    element_to_animations_map_.erase(element_animations->element_id().id);
     element_animations->SetAnimationHost(nullptr);
   }
 
@@ -240,8 +240,10 @@ void AnimationHost::PushPropertiesToImplThread(AnimationHost* host_impl) {
   for (auto& kv : element_to_animations_map_) {
     const auto& element_animations = kv.second;
     if (element_animations->needs_push_properties()) {
+      ElementId element_id;
+      element_id.id = kv.first;
       auto element_animations_impl =
-          host_impl->GetElementAnimationsForElementId(kv.first);
+          host_impl->GetElementAnimationsForElementId(element_id);
       if (element_animations_impl)
         element_animations->PushPropertiesTo(
             std::move(element_animations_impl));
@@ -257,7 +259,7 @@ scoped_refptr<ElementAnimations>
 AnimationHost::GetElementAnimationsForElementId(ElementId element_id) const {
   if (!element_id)
     return nullptr;
-  auto iter = element_to_animations_map_.find(element_id);
+  auto iter = element_to_animations_map_.find(element_id.id);
   return iter == element_to_animations_map_.end() ? nullptr : iter->second;
 }
 
@@ -330,7 +332,7 @@ void AnimationHost::SetAnimationEvents(
     // non-ticking Players may still receive events for impl-only animations.
     const ElementToAnimationsMap& all_element_animations =
         element_to_animations_map_;
-    auto iter = all_element_animations.find(element_id);
+    auto iter = all_element_animations.find(element_id.id);
     if (iter != all_element_animations.end()) {
       switch (events->events_[event_index].type) {
         case AnimationEvent::STARTED: