Change cc::ElementId to be a uint64_t

ui/compositor/layer.cc

Index: ui/compositor/layer.cc
diff --git a/ui/compositor/layer.cc b/ui/compositor/layer.cc
index 64faa6a1418a7f56175b47817e0a521397ef6afe..5fe9b9b3f6b6390e9549cf7f89293b7ccd650da8 100644
--- a/ui/compositor/layer.cc
+++ b/ui/compositor/layer.cc
@@ -617,7 +617,7 @@ void Layer::SwitchToLayer(scoped_refptr<cc::Layer> new_layer) {
   cc_layer_->SetContentsOpaque(fills_bounds_opaquely_);
   cc_layer_->SetIsDrawable(type_ != LAYER_NOT_DRAWN);
   cc_layer_->SetHideLayerAndSubtree(!visible_);
-  cc_layer_->SetElementId(cc::ElementId(cc_layer_->id(), 0));
+  cc_layer_->SetElementId(cc_layer_->id());
 
   SetLayerFilters();
   SetLayerBackgroundFilters();
@@ -1167,7 +1167,7 @@ void Layer::CreateCcLayer() {
   cc_layer_->SetContentsOpaque(true);
   cc_layer_->SetIsDrawable(type_ != LAYER_NOT_DRAWN);
   cc_layer_->SetLayerClient(this);
-  cc_layer_->SetElementId(cc::ElementId(cc_layer_->id(), 0));
+  cc_layer_->SetElementId(cc_layer_->id());
   RecomputePosition();
 }