Use element id's for animations

cc/layers/layer_impl.cc

Index: cc/layers/layer_impl.cc
diff --git a/cc/layers/layer_impl.cc b/cc/layers/layer_impl.cc
index 18562bc1c19fbc0da298083cf3ad6adbe1595510..1ad29f0a51f300aed28b34fbe6e220075691ab15 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -72,7 +72,6 @@ LayerImpl::LayerImpl(LayerTreeImpl* tree_impl, int id)
       scroll_tree_index_(-1),
       sorting_context_id_(0),
       current_draw_mode_(DRAW_MODE_NONE),
-      element_id_(0),
       mutable_properties_(MutableProperty::kNone),
       debug_info_(nullptr),
       scrolls_drawn_descendant_(false),
@@ -815,16 +814,19 @@ bool LayerImpl::HasPotentiallyRunningOpacityAnimation() const {
   return layer_tree_impl_->HasPotentiallyRunningOpacityAnimation(this);
 }
 
-void LayerImpl::SetElementId(uint64_t element_id) {
+void LayerImpl::SetElementId(ElementId element_id) {
   if (element_id == element_id_)
     return;
 
   TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("compositor-worker"),
-               "LayerImpl::SetElementId", "id", element_id);
+               "LayerImpl::SetElementId", "element",
+               element_id.AsValue().release());
 
   layer_tree_impl_->RemoveFromElementMap(this);
   element_id_ = element_id;
   layer_tree_impl_->AddToElementMap(this);
+
+  SetNeedsPushProperties();
 }
 
 void LayerImpl::SetMutableProperties(uint32_t properties) {
@@ -1004,10 +1006,11 @@ void LayerImpl::AsValueInto(base::trace_event::TracedValue* state) const {
   state->SetInteger("gpu_memory_usage",
                     base::saturated_cast<int>(GPUMemoryUsageInBytes()));
 
-  if (mutable_properties_ != MutableProperty::kNone) {
-    state->SetInteger("element_id", base::saturated_cast<int>(element_id_));
+  if (element_id_)
+    element_id_.AddToTracedValue(state);
+
+  if (mutable_properties_ != MutableProperty::kNone)
     state->SetInteger("mutable_properties", mutable_properties_);
-  }
 
   MathUtil::AddToTracedValue("scroll_offset", CurrentScrollOffset(), state);