diff --git a/components/plugins/heapsize.rs b/components/plugins/heapsize.rs
new file mode 100644
index 00000000000..4da8cc070a8
--- /dev/null
+++ b/components/plugins/heapsize.rs
@@ -0,0 +1,54 @@
+
+use syntax::ext::base::{Annotatable, ExtCtxt};
+use syntax::codemap::Span;
+use syntax::ptr::P;
+use syntax::ast::*;
+use syntax::attr::AttrMetaMethods;
+use syntax::ext::build::AstBuilder;
+use syntax::ext::deriving::generic::*;
+
+pub fn expand_heapsize(cx: &mut ExtCtxt, span: Span, mitem: &MetaItem, item: Annotatable, push: &mut FnMut(Annotatable)) {
+    let trait_def = TraitDef {
+        span: span,
+        attributes: Vec::new(),
+        path: ty::Path::new(vec!("util", "mem", "HeapSizeOf")),
+        additional_bounds: Vec::new(),
+        generics: ty::LifetimeBounds::empty(),
+        methods: vec![
+            MethodDef {
+                name: "heap_size_of_children",
+                generics: ty::LifetimeBounds::empty(),
+                explicit_self: ty::borrowed_explicit_self(),
+                args: vec!(),
+                ret_ty: ty::Literal(ty::Path::new_local("usize")),
+                attributes: vec!(),
+                is_unsafe: false,
+                combine_substructure: combine_substructure(Box::new(heapsize_substructure))
+            }
+        ],
+        associated_types: vec![],
+    };
+    trait_def.expand(cx, mitem, &item, push)
+}
+
+fn heapsize_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
+    let fields = match *substr.fields {
+        Struct(ref fs) | EnumMatching(_, _, ref fs) => fs,
+        _ => cx.span_bug(trait_span, "impossible substructure in `heapsize`")
+    };
+
+    fields.iter().fold(cx.expr_usize(trait_span, 0),
+                       |acc, ref item| {
+                        if item.attrs.iter()
+                               .find(|ref a| a.check_name("ignore_heapsize"))
+                               .is_some() {
+                            acc
+                        } else {
+                            cx.expr_binary(item.span, BiAdd, acc,
+                                           cx.expr_method_call(item.span,
+                                                               item.self_.clone(),
+                                                               substr.method_ident,
+                                                               Vec::new()))
+                        }
+                    })
+}
diff --git a/components/plugins/lib.rs b/components/plugins/lib.rs
index 614cce94ab3..6138e4bef84 100644
--- a/components/plugins/lib.rs
+++ b/components/plugins/lib.rs
@@ -8,8 +8,7 @@
 //!
 //!  - `#[privatize]` : Forces all fields in a struct/enum to be private
 //!  - `#[jstraceable]` : Auto-derives an implementation of `JSTraceable` for a struct in the script crate
-//!  - `#[must_root]` : Prevents data of the marked type from being used on the stack. See the lints module for more
-//!     details
+//!  - `#[must_root]` : Prevents data of the marked type from being used on the stack. See the lints module for more details
 //!  - `#[dom_struct]` : Implies `#[privatize]`,`#[jstraceable]`, and `#[must_root]`.
 //!     Use this for structs that correspond to a DOM type
 
@@ -31,6 +30,8 @@ use syntax::parse::token::intern;
 // Public for documentation to show up
 /// Handles the auto-deriving for `#[jstraceable]`
 pub mod jstraceable;
+/// Handles the auto-deriving for `#[heapsize]`
+pub mod heapsize;
 /// Autogenerates implementations of Reflectable on DOM structs
 pub mod reflector;
 pub mod lints;
@@ -43,6 +44,8 @@ pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_syntax_extension(intern("dom_struct"), MultiModifier(box jstraceable::expand_dom_struct));
     reg.register_syntax_extension(intern("jstraceable"), MultiDecorator(box jstraceable::expand_jstraceable));
     reg.register_syntax_extension(intern("_generate_reflector"), MultiDecorator(box reflector::expand_reflector));
+    reg.register_syntax_extension(intern("derive_HeapSizeOf"), MultiDecorator(box heapsize::expand_heapsize));
+    reg.register_syntax_extension(intern("heapsize"), MultiDecorator(box heapsize::expand_heapsize));
     reg.register_macro("to_lower", casing::expand_lower);
     reg.register_macro("to_upper", casing::expand_upper);
     reg.register_lint_pass(box lints::transmute_type::TransmutePass as LintPassObject);
diff --git a/components/util/mem.rs b/components/util/mem.rs
index cd1b9834e48..175863ddb9e 100644
--- a/components/util/mem.rs
+++ b/components/util/mem.rs
@@ -158,3 +158,31 @@ impl<T> Drop for LinkedList2<T> {
     fn drop(&mut self) {}
 }
 
+/// For use on types defined in external crates
+/// with known heap sizes
+#[macro_export]
+macro_rules! known_heap_size(
+    ($size:expr, $($ty:ident),+) => (
+        $(
+            impl $crate::mem::HeapSizeOf for $ty {
+                #[inline]
+                fn heap_size_of_children(&self) -> usize {
+                    $size
+                }
+            }
+        )+
+    );
+    ($size: expr, $ty:ident<$($gen:ident),+>) => (
+        impl<$($gen),+> $crate::mem::HeapSizeOf for $ty<$($gen),+> {
+            #[inline]
+            fn heap_size_of_children(&self) -> usize {
+                $size
+            }
+        }
+    );
+);
+
+
+known_heap_size!(0, u8, u16, u32, u64, usize);
+known_heap_size!(0, i8, i16, i32, i64, isize);
+known_heap_size!(0, bool);
\ No newline at end of file