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/mod.rs

@@ -12,7 +12,6 @@ pub mod import_rule;
 pub mod keyframes_rule;
 mod loader;
 mod media_rule;
-mod memory;
 mod namespace_rule;
 pub mod origin;
 mod page_rule;
@@ -26,6 +25,8 @@ pub mod viewport_rule;
 
 use cssparser::{parse_one_rule, Parser, ParserInput};
 use error_reporting::NullReporter;
+#[cfg(feature = "gecko")]
+use malloc_size_of::MallocSizeOfOps;
 use parser::{ParserContext, ParserErrorContext};
 use servo_arc::Arc;
 use shared_lock::{DeepCloneParams, DeepCloneWithLock, Locked, SharedRwLock, SharedRwLockReadGuard, ToCssWithGuard};
@@ -40,10 +41,6 @@ pub use self::import_rule::ImportRule;
 pub use self::keyframes_rule::KeyframesRule;
 pub use self::loader::StylesheetLoader;
 pub use self::media_rule::MediaRule;
-pub use self::memory::{MallocEnclosingSizeOfFn, MallocSizeOf, MallocSizeOfBox, MallocSizeOfFn};
-pub use self::memory::{MallocSizeOfHash, MallocSizeOfVec, MallocSizeOfWithGuard};
-#[cfg(feature = "gecko")]
-pub use self::memory::{MallocSizeOfWithRepeats, SizeOfState};
 pub use self::namespace_rule::NamespaceRule;
 pub use self::origin::{Origin, OriginSet, PerOrigin, PerOriginIter};
 pub use self::page_rule::PageRule;
@@ -109,12 +106,10 @@ pub enum CssRule {
     Document(Arc<Locked<DocumentRule>>),
 }
 
-impl MallocSizeOfWithGuard for CssRule {
-    fn malloc_size_of_children(
-        &self,
-        guard: &SharedRwLockReadGuard,
-        malloc_size_of: MallocSizeOfFn
-    ) -> usize {
+impl CssRule {
+    /// Measure heap usage.
+    #[cfg(feature = "gecko")]
+    fn size_of(&self, guard: &SharedRwLockReadGuard, ops: &mut MallocSizeOfOps) -> usize {
         match *self {
             // Not all fields are currently fully measured. Extra measurement
             // may be added later.
@@ -125,13 +120,9 @@ impl MallocSizeOfWithGuard for CssRule {
             // it on the C++ side in the child list of the ServoStyleSheet.
             CssRule::Import(_) => 0,
 
-            CssRule::Style(ref lock) => {
-                lock.read_with(guard).malloc_size_of_children(guard, malloc_size_of)
-            },
+            CssRule::Style(ref lock) => lock.read_with(guard).size_of(guard, ops),
 
-            CssRule::Media(ref lock) => {
-                lock.read_with(guard).malloc_size_of_children(guard, malloc_size_of)
-            },
+            CssRule::Media(ref lock) => lock.read_with(guard).size_of(guard, ops),
 
             CssRule::FontFace(_) => 0,
             CssRule::FontFeatureValues(_) => 0,
@@ -139,17 +130,11 @@ impl MallocSizeOfWithGuard for CssRule {
             CssRule::Viewport(_) => 0,
             CssRule::Keyframes(_) => 0,
 
-            CssRule::Supports(ref lock) => {
-                lock.read_with(guard).malloc_size_of_children(guard, malloc_size_of)
-            },
+            CssRule::Supports(ref lock) => lock.read_with(guard).size_of(guard, ops),
 
-            CssRule::Page(ref lock) => {
-                lock.read_with(guard).malloc_size_of_children(guard, malloc_size_of)
-            },
+            CssRule::Page(ref lock) => lock.read_with(guard).size_of(guard, ops),
 
-            CssRule::Document(ref lock) => {
-                lock.read_with(guard).malloc_size_of_children(guard, malloc_size_of)
-            },
+            CssRule::Document(ref lock) => lock.read_with(guard).size_of(guard, ops),
         }
     }
 }