style: Measure heap allocations hanging off selector components.

Bug: 1475191
Reviewed-by: emilio
MozReview-Commit-ID: D7vZQ7v8owS

components/malloc_size_of/lib.rs

@@ -693,6 +693,90 @@ impl MallocSizeOf for selectors::parser::AncestorHashes {
     }
 }
 
+impl<Impl: selectors::parser::SelectorImpl> MallocSizeOf
+    for selectors::parser::Selector<Impl>
+where
+    Impl::NonTSPseudoClass: MallocSizeOf,
+    Impl::PseudoElement: MallocSizeOf,
+{
+    fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+        let mut n = 0;
+
+        // It's OK to measure this ThinArc directly because it's the
+        // "primary" reference. (The secondary references are on the
+        // Stylist.)
+        n += unsafe { ops.malloc_size_of(self.thin_arc_heap_ptr()) };
+        for component in self.iter_raw_match_order() {
+            n += component.size_of(ops);
+        }
+
+        n
+    }
+}
+
+impl<Impl: selectors::parser::SelectorImpl> MallocSizeOf
+    for selectors::parser::Component<Impl>
+where
+    Impl::NonTSPseudoClass: MallocSizeOf,
+    Impl::PseudoElement: MallocSizeOf,
+{
+    fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+        use selectors::parser::Component;
+
+        match self {
+            Component::AttributeOther(ref attr_selector) => {
+                attr_selector.size_of(ops)
+            }
+            Component::Negation(ref components) => {
+                components.size_of(ops)
+            }
+            Component::NonTSPseudoClass(ref pseudo) => {
+                (*pseudo).size_of(ops)
+            }
+            Component::Slotted(ref selector) |
+            Component::Host(Some(ref selector)) => {
+                selector.size_of(ops)
+            }
+            Component::PseudoElement(ref pseudo) => {
+                (*pseudo).size_of(ops)
+            }
+            Component::Combinator(..) |
+            Component::ExplicitAnyNamespace |
+            Component::ExplicitNoNamespace |
+            Component::DefaultNamespace(..) |
+            Component::Namespace(..) |
+            Component::ExplicitUniversalType |
+            Component::LocalName(..) |
+            Component::ID(..) |
+            Component::Class(..) |
+            Component::AttributeInNoNamespaceExists { .. } |
+            Component::AttributeInNoNamespace { .. } |
+            Component::FirstChild |
+            Component::LastChild |
+            Component::OnlyChild |
+            Component::Root |
+            Component::Empty |
+            Component::Scope |
+            Component::NthChild(..) |
+            Component::NthLastChild(..) |
+            Component::NthOfType(..) |
+            Component::NthLastOfType(..) |
+            Component::FirstOfType |
+            Component::LastOfType |
+            Component::OnlyOfType |
+            Component::Host(None) => 0,
+        }
+    }
+}
+
+impl<Impl: selectors::parser::SelectorImpl> MallocSizeOf
+    for selectors::attr::AttrSelectorWithNamespace<Impl>
+{
+    fn size_of(&self, _ops: &mut MallocSizeOfOps) -> usize {
+        0
+    }
+}
+
 impl MallocSizeOf for Void {
     #[inline]
     fn size_of(&self, _ops: &mut MallocSizeOfOps) -> usize {