Fix unused import warnings in geckolib

ports/geckolib/properties.mako.rs

@@ -20,7 +20,6 @@ use gecko_bindings::bindings::{Gecko_CopyMozBindingFrom, Gecko_CopyListStyleType
 use gecko_bindings::bindings::{Gecko_SetMozBinding, Gecko_SetListStyleType};
 use gecko_bindings::structs;
 use glue::ArcHelpers;
-use heapsize::HeapSizeOf;
 use std::fmt::{self, Debug};
 use std::mem::{transmute, zeroed};
 use std::sync::Arc;

ports/geckolib/wrapper.rs

@@ -41,6 +41,7 @@ use style::dom::{TDocument, TElement, TNode, TRestyleDamage, UnsafeNode};
 use style::element_state::ElementState;
 #[allow(unused_imports)] // Used in commented-out code.
 use style::error_reporting::StdoutErrorReporter;
+#[allow(unused_imports)] // Used in commented-out code.
 use style::parser::ParserContextExtraData;
 use style::properties::{PropertyDeclaration, PropertyDeclarationBlock};
 #[allow(unused_imports)] // Used in commented-out code.