diff --git a/dom/bindings/Codegen.py b/dom/bindings/Codegen.py
index e66bef653b60..05f895f1cd74 100644
--- a/dom/bindings/Codegen.py
+++ b/dom/bindings/Codegen.py
@@ -5801,7 +5801,8 @@ class CGMemberJITInfo(CGThing):
             # while we have the right type.
             getter = ("(JSJitGetterOp)get_%s" % self.member.identifier.name)
             getterinfal = "infallible" in self.descriptor.getExtendedAttributes(self.member, getter=True)
-            getterconst = self.member.getExtendedAttribute("Constant")
+            getterconst = (self.member.getExtendedAttribute("SameObject") or
+                           self.member.getExtendedAttribute("Constant"))
             getterpure = getterconst or self.member.getExtendedAttribute("Pure")
             assert (getterinfal or (not getterconst and not getterpure))
 
diff --git a/dom/bindings/parser/WebIDL.py b/dom/bindings/parser/WebIDL.py
index 88c88a3afd04..a76827e85ce3 100644
--- a/dom/bindings/parser/WebIDL.py
+++ b/dom/bindings/parser/WebIDL.py
@@ -2601,6 +2601,10 @@ class IDLAttribute(IDLInterfaceMember):
             raise WebIDLError("An attribute with [PutForwards] must have an "
                               "interface type as its type", [self.location])
 
+        if not self.type.isInterface() and self.getExtendedAttribute("SameObject"):
+            raise WebIDLError("An attribute with [SameObject] must have an "
+                              "interface type as its type", [self.location])
+
     def validate(self):
         pass
 
@@ -2615,12 +2619,14 @@ class IDLAttribute(IDLInterfaceMember):
                               [self.location])
         elif (((identifier == "Throws" or identifier == "GetterThrows") and
                (self.getExtendedAttribute("Pure") or
+                self.getExtendedAttribute("SameObject") or
                 self.getExtendedAttribute("Constant"))) or
-              ((identifier == "Pure" or identifier == "Constant") and
+              ((identifier == "Pure" or identifier == "SameObject" or
+                identifier == "Constant") and
                (self.getExtendedAttribute("Throws") or
                 self.getExtendedAttribute("GetterThrows")))):
-            raise WebIDLError("Throwing things can't be [Pure] or [Constant]",
-                              [attr.location])
+            raise WebIDLError("Throwing things can't be [Pure] or [Constant] "
+                              "or [SameObject]", [attr.location])
         elif identifier == "LenientThis":
             if not attr.noArguments():
                 raise WebIDLError("[LenientThis] must take no arguments",
@@ -2637,6 +2643,9 @@ class IDLAttribute(IDLInterfaceMember):
                 raise WebIDLError("[Unforgeable] is only allowed on non-static "
                                   "attributes", [attr.location, self.location])
             self._unforgeable = True
+        elif identifier == "SameObject" and not self.readonly:
+            raise WebIDLError("[SameObject] only allowed on readonly attributes",
+                              [attr.location, self.location])
         elif identifier == "Constant" and not self.readonly:
             raise WebIDLError("[Constant] only allowed on readonly attributes",
                               [attr.location, self.location])
@@ -2673,6 +2682,7 @@ class IDLAttribute(IDLInterfaceMember):
               identifier == "Throws" or
               identifier == "GetterThrows" or
               identifier == "ChromeOnly" or
+              identifier == "SameObject" or
               identifier == "Constant" or
               identifier == "Func" or
               identifier == "Creator"):
@@ -3196,6 +3206,9 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
             raise WebIDLError("Methods must not be flagged as "
                               "[Unforgeable]",
                               [attr.location, self.location])
+        elif identifier == "SameObject":
+            raise WebIDLError("Methods must not be flagged as [SameObject]",
+                              [attr.location, self.location]);
         elif identifier == "Constant":
             raise WebIDLError("Methods must not be flagged as [Constant]",
                               [attr.location, self.location]);
diff --git a/dom/bindings/parser/tests/test_attr.py b/dom/bindings/parser/tests/test_attr.py
index 698be3f309b4..fb0c91964609 100644
--- a/dom/bindings/parser/tests/test_attr.py
+++ b/dom/bindings/parser/tests/test_attr.py
@@ -313,3 +313,29 @@ def WebIDLTest(parser, harness):
     except Exception, x:
         threw = True
     harness.ok(threw, "Should spell [Throws] correctly")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+          interface A {
+            [SameObject] readonly attribute boolean foo;
+          };
+        """)
+        results = parser.finish()
+    except Exception, x:
+        threw = True
+    harness.ok(threw, "Should not allow [SameObject] on attributes not of interface type")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+          interface A {
+            [SameObject] readonly attribute A foo;
+          };
+        """)
+        results = parser.finish()
+    except Exception, x:
+        threw = True
+    harness.ok(not threw, "Should allow [SameObject] on attributes of interface type")
diff --git a/dom/webidl/Element.webidl b/dom/webidl/Element.webidl
index e837e867afc9..5115574849bc 100644
--- a/dom/webidl/Element.webidl
+++ b/dom/webidl/Element.webidl
@@ -35,7 +35,7 @@ interface Element : Node {
   [Constant]
   readonly attribute DOMTokenList? classList;
 
-  [Constant]
+  [SameObject]
   readonly attribute MozNamedAttrMap attributes;
   DOMString? getAttribute(DOMString name);
   DOMString? getAttributeNS(DOMString? namespace, DOMString localName);
diff --git a/dom/webidl/Node.webidl b/dom/webidl/Node.webidl
index 2002d647a306..06f54afb0429 100644
--- a/dom/webidl/Node.webidl
+++ b/dom/webidl/Node.webidl
@@ -42,7 +42,7 @@ interface Node : EventTarget {
   [Pure]
   readonly attribute Element? parentElement;
   boolean hasChildNodes();
-  [Constant]
+  [SameObject]
   readonly attribute NodeList childNodes;
   [Pure]
   readonly attribute Node? firstChild;