Make script build without impl<T: HeapSizeOf> HeapSizeOf for Arc<T>.

The removal of this impl is not included in this commit.
CC https://github.com/servo/heapsize/issues/37#issuecomment-249861171

components/script/dom/document.rs

@@ -146,6 +146,14 @@ enum ParserBlockedByScript {
     Unblocked,
 }
 
+#[derive(JSTraceable, HeapSizeOf)]
+#[must_root]
+struct StylesheetInDocument {
+    node: JS<Node>,
+    #[ignore_heap_size_of = "Arc"]
+    stylesheet: Arc<Stylesheet>,
+}
+
 // https://dom.spec.whatwg.org/#document
 #[dom_struct]
 pub struct Document {
@@ -174,7 +182,7 @@ pub struct Document {
     anchors: MutNullableHeap<JS<HTMLCollection>>,
     applets: MutNullableHeap<JS<HTMLCollection>>,
     /// List of stylesheets associated with nodes in this document. |None| if the list needs to be refreshed.
-    stylesheets: DOMRefCell<Option<Vec<(JS<Node>, Arc<Stylesheet>)>>>,
+    stylesheets: DOMRefCell<Option<Vec<StylesheetInDocument>>>,
     /// Whether the list of stylesheets has changed since the last reflow was triggered.
     stylesheets_changed_since_reflow: Cell<bool>,
     ready_state: Cell<DocumentReadyState>,
@@ -1891,13 +1899,16 @@ impl Document {
                             node.get_stylesheet()
                         } else {
                             None
-                        }.map(|stylesheet| (JS::from_ref(&*node), stylesheet))
+                        }.map(|stylesheet| StylesheetInDocument {
+                            node: JS::from_ref(&*node),
+                            stylesheet: stylesheet
+                        })
                     })
                     .collect());
             };
         }
         self.stylesheets.borrow().as_ref().unwrap().iter()
-                        .map(|&(_, ref stylesheet)| stylesheet.clone())
+                        .map(|s| s.stylesheet.clone())
                         .collect()
     }
 

components/script/dom/element.rs

@@ -109,6 +109,7 @@ pub struct Element {
     prefix: Option<DOMString>,
     attrs: DOMRefCell<Vec<JS<Attr>>>,
     id_attribute: DOMRefCell<Option<Atom>>,
+    #[ignore_heap_size_of = "Arc"]
     style_attribute: DOMRefCell<Option<Arc<PropertyDeclarationBlock>>>,
     attr_list: MutNullableHeap<JS<NamedNodeMap>>,
     class_list: MutNullableHeap<JS<DOMTokenList>>,

components/script/dom/htmlimageelement.rs

@@ -47,6 +47,7 @@ struct ImageRequest {
     state: State,
     parsed_url: Option<Url>,
     source_url: Option<DOMString>,
+    #[ignore_heap_size_of = "Arc"]
     image: Option<Arc<Image>>,
     metadata: Option<ImageMetadata>,
 }

components/script/dom/htmllinkelement.rs

@@ -52,6 +52,7 @@ no_jsmanaged_fields!(Stylesheet);
 pub struct HTMLLinkElement {
     htmlelement: HTMLElement,
     rel_list: MutNullableHeap<JS<DOMTokenList>>,
+    #[ignore_heap_size_of = "Arc"]
     stylesheet: DOMRefCell<Option<Arc<Stylesheet>>>,
 
     /// https://html.spec.whatwg.org/multipage/#a-style-sheet-that-is-blocking-scripts

components/script/dom/htmlmetaelement.rs

@@ -27,6 +27,7 @@ use style::viewport::ViewportRule;
 #[dom_struct]
 pub struct HTMLMetaElement {
     htmlelement: HTMLElement,
+    #[ignore_heap_size_of = "Arc"]
     stylesheet: DOMRefCell<Option<Arc<Stylesheet>>>,
 }
 

components/script/dom/htmlobjectelement.rs

@@ -24,6 +24,7 @@ use string_cache::Atom;
 #[dom_struct]
 pub struct HTMLObjectElement {
     htmlelement: HTMLElement,
+    #[ignore_heap_size_of = "Arc"]
     image: DOMRefCell<Option<Arc<Image>>>,
 }
 

components/script/dom/htmlstyleelement.rs

@@ -24,6 +24,7 @@ use style::stylesheets::{Stylesheet, Origin};
 #[dom_struct]
 pub struct HTMLStyleElement {
     htmlelement: HTMLElement,
+    #[ignore_heap_size_of = "Arc"]
     stylesheet: DOMRefCell<Option<Arc<Stylesheet>>>,
 }
 

components/script/dom/workerglobalscope.rs

@@ -83,6 +83,7 @@ pub struct WorkerGlobalScope {
     worker_id: WorkerId,
     pipeline_id: PipelineId,
     worker_url: Url,
+    #[ignore_heap_size_of = "Arc"]
     closing: Option<Arc<AtomicBool>>,
     #[ignore_heap_size_of = "Defined in js"]
     runtime: Runtime,