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/stylesheets/keyframes_rule.rs

@@ -19,7 +19,7 @@ use shared_lock::{DeepCloneParams, DeepCloneWithLock, SharedRwLock, SharedRwLock
 use std::fmt;
 use style_traits::{PARSING_MODE_DEFAULT, ToCss, ParseError, StyleParseError};
 use style_traits::PropertyDeclarationParseError;
-use stylesheets::{CssRuleType, MallocSizeOfFn, MallocSizeOfVec, StylesheetContents};
+use stylesheets::{CssRuleType, StylesheetContents};
 use stylesheets::rule_parser::{VendorPrefix, get_location_with_offset};
 use values::{KeyframesName, serialize_percentage};
 
@@ -100,6 +100,7 @@ impl DeepCloneWithLock for KeyframesRule {
 /// A number from 0 to 1, indicating the percentage of the animation when this
 /// keyframe should run.
 #[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
+#[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct KeyframePercentage(pub f32);
 
@@ -263,11 +264,14 @@ impl DeepCloneWithLock for Keyframe {
 ///
 /// TODO: Find a better name for this?
 #[derive(Debug)]
+#[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub enum KeyframesStepValue {
     /// A step formed by a declaration block specified by the CSS.
     Declarations {
         /// The declaration block per se.
+        #[cfg_attr(feature = "gecko",
+                   ignore_malloc_size_of = "XXX: Primary ref, measure if DMD says it's worthwhile")]
         #[cfg_attr(feature = "servo", ignore_heap_size_of = "Arc")]
         block: Arc<Locked<PropertyDeclarationBlock>>
     },
@@ -278,6 +282,7 @@ pub enum KeyframesStepValue {
 
 /// A single step from a keyframe animation.
 #[derive(Debug)]
+#[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct KeyframesStep {
     /// The percentage of the animation duration when this step starts.
@@ -349,6 +354,7 @@ impl KeyframesStep {
 ///
 /// It only takes into account animable properties.
 #[derive(Debug)]
+#[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct KeyframesAnimation {
     /// The difference steps of the animation.
@@ -442,14 +448,6 @@ impl KeyframesAnimation {
 
         result
     }
-
-    /// Measure heap usage.
-    pub fn malloc_size_of_children(&self, malloc_size_of: MallocSizeOfFn) -> usize {
-        let mut n = 0;
-        n += self.steps.malloc_shallow_size_of_vec(malloc_size_of);
-        n += self.properties_changed.malloc_shallow_size_of_vec(malloc_size_of);
-        n
-    }
 }
 
 /// Parses a keyframes list, like: