Implement [Unforgeable]

This is mostly stolen from Gecko. As there, we define the unforgeable members
on an object stored in the slots of the prototype object. They are then copied
onto instance objects when they are instantiated. It should be noted that
proxy objects see their unforgeable memebers defined on their expando object.

Unforgeable attributes aren't properly inherited in codegen (in a similar
fashion as getters and setters as filed in #5875) and require to be redefined
in derived interfaces. Fortunately, there are currently no such interfaces.

No unforgeable members can be included into the TestBinding interfaces for good
measure because they are not compatible with setters.

Given the unforgeable holder object has the same prototype as actual instances
of the interface, the finalize hook needs to check its slot pointer for nullity
before dropping it.

The new failing test isn't related to Unforgeable attributes, but to the fact
that all Document instances currently have a Location, even if their window
isn't in a browsing context.

1 files changed, 8 insertions, 0 deletions

diff --git a/components/script/dom/bindings/utils.rs b/components/script/dom/bindings/utils.rs
index 97d5bb12eba..fe7c8030baa 100644
--- a/components/script/dom/bindings/utils.rs
+++ b/components/script/dom/bindings/utils.rs
@@ -78,6 +78,10 @@ impl GlobalStaticData {
     }
 }
 
+/// The index of the slot where the object holder of that interface's
+/// unforgeable members are defined.
+pub const DOM_PROTO_UNFORGEABLE_HOLDER_SLOT: u32 = 0;
+
 /// The index of the slot that contains a reference to the ProtoOrIfaceArray.
 // All DOM globals must have a slot at DOM_PROTOTYPE_SLOT.
 pub const DOM_PROTOTYPE_SLOT: u32 = js::JSCLASS_GLOBAL_SLOT_COUNT;
@@ -181,8 +185,12 @@ pub fn get_proto_or_iface_array(global: *mut JSObject) -> *mut ProtoOrIfaceArray
 pub struct NativeProperties {
     /// Instance methods for the interface.
     pub methods: Option<&'static [JSFunctionSpec]>,
+    /// Unforgeable instance methods for the interface.
+    pub unforgeable_methods: Option<&'static [JSFunctionSpec]>,
     /// Instance attributes for the interface.
     pub attrs: Option<&'static [JSPropertySpec]>,
+    /// Unforgeable instance attributes for the interface.
+    pub unforgeable_attrs: Option<&'static [JSPropertySpec]>,
     /// Constants for the interface.
     pub consts: Option<&'static [ConstantSpec]>,
     /// Static methods for the interface.