Overhaul MallocSizeOf and related things.

This patch makes the MallocSizeOf stuff in Stylo work more like the HeapSizeOf
stuff already in Servo, except better. In particular, it adds deriving support
for MallocSizeOf, which will make it easier to improve coverage.

The patch does the following.

- Combines servo/components/style/stylesheets/memory.rs and the heapsize crate
  into a new crate, malloc_size_of.

- Forks the heapsize_derive crate, calling it malloc_size_of, so that
  MallocSizeOf can be derived.

- Both the new crates have MIT/Apache licenses, like heapsize, in case they are
  incorporated into heapsize in the future.

- Renames the methods within MallocSizeOf and the related traits so they are
  more concise.

- Removes MallocSizeOfWithGuard.

- Adds `derive(MallocSizeOf)` to a lot of types, in some cases replacing an
  equivalent or almost-equivalent hand-written implementation.

- Adds stuff so that Rc/Arc can be handled properly.

components/style/invalidation/element/invalidation_map.rs

@@ -16,8 +16,6 @@ use selectors::parser::{Combinator, Component};
 use selectors::parser::{Selector, SelectorIter, SelectorMethods};
 use selectors::visitor::SelectorVisitor;
 use smallvec::SmallVec;
-#[cfg(feature = "gecko")]
-use stylesheets::{MallocEnclosingSizeOfFn, MallocSizeOfFn, MallocSizeOfHash, MallocSizeOfVec};
 
 #[cfg(feature = "gecko")]
 /// Gets the element state relevant to the given `:dir` pseudo-class selector.
@@ -58,11 +56,15 @@ pub fn dir_selector_to_state(s: &[u16]) -> ElementState {
 /// rules and determine the maximum effect that a given state or attribute
 /// change may have on the style of elements in the document.
 #[derive(Clone, Debug)]
+#[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct Dependency {
     /// The dependency selector.
+    #[cfg_attr(feature = "gecko",
+               ignore_malloc_size_of = "CssRules have primary refs, we measure there")]
     #[cfg_attr(feature = "servo", ignore_heap_size_of = "Arc")]
     pub selector: Selector<SelectorImpl>,
+
     /// The offset into the selector that we should match on.
     pub selector_offset: usize,
 }
@@ -114,6 +116,7 @@ impl SelectorMapEntry for Dependency {
 /// The same, but for state selectors, which can track more exactly what state
 /// do they track.
 #[derive(Clone, Debug)]
+#[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct StateDependency {
     /// The other dependency fields.
@@ -137,6 +140,7 @@ impl SelectorMapEntry for StateDependency {
 /// selectors the better, so this looks up by id, class, or looks at the list of
 /// state/other attribute affecting selectors.
 #[derive(Debug)]
+#[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct InvalidationMap {
     /// A map from a given class name to all the selectors with that class
@@ -295,34 +299,6 @@ impl InvalidationMap {
 
         Ok(())
     }
-
-    /// Measures heap usage.
-    #[cfg(feature = "gecko")]
-    pub fn malloc_size_of_children(&self, malloc_size_of: MallocSizeOfFn,
-                                   malloc_enclosing_size_of: MallocEnclosingSizeOfFn)
-                                   -> usize {
-        // Currently we measure the HashMap storage, but not things pointed to
-        // by keys and values.
-        let mut n = 0;
-
-        n += self.class_to_selector.malloc_shallow_size_of_hash(malloc_enclosing_size_of);
-        for (_, val) in self.class_to_selector.iter() {
-            n += val.malloc_shallow_size_of_vec(malloc_size_of);
-        }
-
-        n += self.id_to_selector.malloc_shallow_size_of_hash(malloc_enclosing_size_of);
-        for (_, val) in self.id_to_selector.iter() {
-            n += val.malloc_shallow_size_of_vec(malloc_size_of);
-        }
-
-        n += self.state_affecting_selectors.malloc_size_of_children(malloc_size_of,
-                                                                    malloc_enclosing_size_of);
-
-        n += self.other_attribute_affecting_selectors.malloc_size_of_children(
-            malloc_size_of, malloc_enclosing_size_of);
-
-        n
-    }
 }
 
 /// A struct that collects invalidations for a given compound selector.