Cache legacy callback interface objects in proto_or_icache_array

We need them to be cached to not instantiate them multiple times with
lazy initialisation.

components/script/dom/bindings/codegen/CodegenRust.py

@@ -2379,9 +2379,8 @@ class CGCreateInterfaceObjectsMethod(CGAbstractMethod):
     properties should be a PropertyArrays instance.
     """
     def __init__(self, descriptor, properties):
-        args = [Argument('*mut JSContext', 'cx'), Argument('HandleObject', 'global')]
-        if not descriptor.interface.isCallback():
-            args.append(Argument('*mut ProtoOrIfaceArray', 'cache'))
+        args = [Argument('*mut JSContext', 'cx'), Argument('HandleObject', 'global'),
+                Argument('*mut ProtoOrIfaceArray', 'cache')]
         CGAbstractMethod.__init__(self, descriptor, 'CreateInterfaceObjects', 'void', args,
                                   unsafe=True)
         self.properties = properties
@@ -2391,7 +2390,14 @@ def definition_body(self):
         if self.descriptor.interface.isCallback():
             assert not self.descriptor.interface.ctor() and self.descriptor.interface.hasConstants()
             return CGGeneric("""\
-create_callback_interface_object(cx, global, sConstants, %s);""" % str_to_const_array(name))
+let mut interface = RootedObject::new(cx, ptr::null_mut());
+create_callback_interface_object(cx, global, sConstants, %(name)s, interface.handle_mut());
+assert!(!interface.ptr.is_null());
+(*cache)[PrototypeList::Constructor::%(id)s as usize] = interface.ptr;
+if <*mut JSObject>::needs_post_barrier(interface.ptr) {
+    <*mut JSObject>::post_barrier((*cache).as_mut_ptr().offset(PrototypeList::Constructor::%(id)s as isize));
+}
+""" % {"id": name, "name": str_to_const_array(name)})
 
         if len(self.descriptor.prototypeChain) == 1:
             if self.descriptor.interface.getExtendedAttribute("ExceptionClass"):
@@ -2672,14 +2678,14 @@ def define(self):
 
     def definition_body(self):
         if self.descriptor.interface.isCallback():
-            code = "CreateInterfaceObjects(cx, global);"
+            function = "GetConstructorObject"
         else:
-            code = """\
+            function = "GetProtoObject"
+        return CGGeneric("""\
+assert!(!global.get().is_null());
 let mut proto = RootedObject::new(cx, ptr::null_mut());
-GetProtoObject(cx, global, proto.handle_mut());
-assert!(!proto.ptr.is_null());
-"""
-        return CGGeneric("assert!(!global.get().is_null());\n" + code)
+%s(cx, global, proto.handle_mut());
+assert!(!proto.ptr.is_null());""" % function)
 
 
 def needCx(returnType, arguments, considerTypes):
@@ -4956,7 +4962,8 @@ def __init__(self, descriptor):
         cgThings = []
         if not descriptor.interface.isCallback():
             cgThings.append(CGGetProtoObjectMethod(descriptor))
-        if descriptor.interface.hasInterfaceObject() and descriptor.hasDescendants():
+        if (descriptor.interface.hasInterfaceObject() and
+                descriptor.shouldHaveGetConstructorObjectMethod()):
             cgThings.append(CGGetConstructorObjectMethod(descriptor))
 
         for m in descriptor.interface.members:
@@ -6093,7 +6100,8 @@ def PrototypeList(config):
         # Prototype ID enum.
         interfaces = config.getDescriptors(isCallback=False)
         protos = [d.name for d in interfaces]
-        constructors = [d.name for d in interfaces if d.hasDescendants()]
+        constructors = [d.name for d in config.getDescriptors(hasInterfaceObject=True)
+                        if d.shouldHaveGetConstructorObjectMethod()]
         proxies = [d.name for d in config.getDescriptors(proxy=True)]
 
         return CGList([

components/script/dom/bindings/codegen/Configuration.py

@@ -345,6 +345,10 @@ def hasDescendants(self):
         return (self.interface.getUserData("hasConcreteDescendant", False) or
                 self.interface.getUserData("hasProxyDescendant", False))
 
+    def shouldHaveGetConstructorObjectMethod(self):
+        assert self.interface.hasInterfaceObject()
+        return self.interface.isCallback() or self.hasDescendants()
+
     def isGlobal(self):
         """
         Returns true if this is the primary interface for a global object

components/script/dom/bindings/interface.rs

@@ -178,13 +178,14 @@ pub unsafe fn create_callback_interface_object(
         cx: *mut JSContext,
         receiver: HandleObject,
         constants: &'static [ConstantSpec],
-        name: &'static [u8]) {
+        name: &'static [u8],
+        rval: MutableHandleObject) {
     assert!(!constants.is_empty());
-    let interface_object = RootedObject::new(cx, JS_NewObject(cx, ptr::null()));
-    assert!(!interface_object.ptr.is_null());
-    define_constants(cx, interface_object.handle(), constants);
-    define_name(cx, interface_object.handle(), name);
-    define_on_global_object(cx, receiver, name, interface_object.handle());
+    rval.set(JS_NewObject(cx, ptr::null()));
+    assert!(!rval.ptr.is_null());
+    define_constants(cx, rval.handle(), constants);
+    define_name(cx, rval.handle(), name);
+    define_on_global_object(cx, receiver, name, rval.handle());
 }
 
 /// Create the interface prototype object of a non-callback interface.