--- a/dom/bindings/Bindings.conf
+++ b/dom/bindings/Bindings.conf
@@ -503,17 +503,18 @@ DOMInterfaces = {
                                'ReceiveWeakCallbackInterface',
                                'ReceiveWeakNullableCallbackInterface',
                                'receiveWeakCastableObjectSequence',
                                'receiveWeakNullableCastableObjectSequence',
                                'receiveWeakCastableObjectNullableSequence',
                                'receiveWeakNullableCastableObjectNullableSequence' ],
         'binaryNames': { 'methodRenamedFrom': 'methodRenamedTo',
                          'attributeGetterRenamedFrom': 'attributeGetterRenamedTo',
-                         'attributeRenamedFrom': 'attributeRenamedTo' }
+                         'attributeRenamedFrom': 'attributeRenamedTo',
+                         '__stringifier' : 'Stringify' }
         },
 
 'TestNonCastableInterface' : {
         'headerFile': 'TestBindingHeader.h',
         'register': False,
         'castable': False
         },
 

--- a/dom/bindings/parser/WebIDL.py
+++ b/dom/bindings/parser/WebIDL.py
@@ -595,45 +595,49 @@ class IDLInterface(IDLObjectWithScope):
             self.members.extend(additionalMembers)
 
         for ancestor in self.getInheritedInterfaces():
             ancestor.interfacesBasedOnSelf.add(self)
             for ancestorConsequential in ancestor.getConsequentialInterfaces():
                 ancestorConsequential.interfacesBasedOnSelf.add(self)
 
         # Ensure that there's at most one of each {named,indexed}
-        # {getter,setter,creator,deleter}.
-        specialMembersSeen = set()
+        # {getter,setter,creator,deleter} and at most one stringifier.
+        specialMembersSeen = {}
         for member in self.members:
             if not member.isMethod():
                 continue
 
             if member.isGetter():
                 memberType = "getters"
             elif member.isSetter():
                 memberType = "setters"
             elif member.isCreator():
                 memberType = "creators"
             elif member.isDeleter():
                 memberType = "deleters"
+            elif member.isStringifier():
+                memberType = "stringifiers"
             else:
                 continue
 
-            if member.isNamed():
-                memberType = "named " + memberType
-            elif member.isIndexed():
-                memberType = "indexed " + memberType
-            else:
-                continue
+            if memberType != "stringifiers":
+                if member.isNamed():
+                    memberType = "named " + memberType
+                else:
+                    assert member.isIndexed()
+                    memberType = "indexed " + memberType
 
             if memberType in specialMembersSeen:
                 raise WebIDLError("Multiple " + memberType + " on %s" % (self),
-                                   [self.location])
-
-            specialMembersSeen.add(memberType)
+                                   [self.location,
+                                    specialMembersSeen[memberType].location,
+                                    member.location])
+
+            specialMembersSeen[memberType] = member
 
     def validate(self):
         for member in self.members:
             member.validate()
 
             # Check that PutForwards refers to another attribute and that no
             # cycles exist in forwarded assignments.
             if member.isAttr():
@@ -3294,16 +3298,30 @@ class Parser(Tokenizer):
                  "stringifier" if stringifier else ""), allowDoubleUnderscore=True)
 
         method = IDLMethod(self.getLocation(p, 2), identifier, returnType, arguments,
                            static=static, getter=getter, setter=setter, creator=creator,
                            deleter=deleter, specialType=specialType,
                            legacycaller=legacycaller, stringifier=stringifier)
         p[0] = method
 
+    def p_Stringifier(self, p):
+        """
+            Operation : STRINGIFIER SEMICOLON
+        """
+        identifier = IDLUnresolvedIdentifier(BuiltinLocation("<auto-generated-identifier>"),
+                                             "__stringifier",
+                                             allowDoubleUnderscore=True)
+        method = IDLMethod(self.getLocation(p, 1),
+                           identifier,
+                           returnType=BuiltinTypes[IDLBuiltinType.Types.domstring],
+                           arguments=[],
+                           stringifier=True)
+        p[0] = method
+
     def p_QualifierStatic(self, p):
         """
             Qualifier : STATIC
         """
         p[0] = [IDLInterfaceMember.Special.Static]
 
     def p_QualifierStringifier(self, p):
         """

new file mode 100644
--- /dev/null
+++ b/dom/bindings/parser/tests/test_stringifier.py
@@ -0,0 +1,46 @@
+import WebIDL
+
+def WebIDLTest(parser, harness):
+    parser.parse("""
+        interface TestStringifier {
+          stringifier;
+        };
+    """)
+
+    results = parser.finish()
+
+    harness.ok(isinstance(results[0].members[0], WebIDL.IDLMethod),
+               "Stringifer should be method")
+
+    parser = parser.reset()
+
+    threw = False
+    try:
+        parser.parse("""
+            interface TestStringifier {
+              stringifier;
+              stringifier;
+            };
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should not allow two 'stringifier;'")
+
+    parser = parser.reset()
+
+    threw = False
+    try:
+        parser.parse("""
+            interface TestStringifier {
+              stringifier;
+              stringifier DOMString foo();
+            };
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should not allow a 'stringifier;' and a 'stringifier()'")
+

--- a/dom/bindings/test/TestBindingHeader.h
+++ b/dom/bindings/test/TestBindingHeader.h
@@ -433,16 +433,17 @@ public:
   static bool StaticAttribute(nsISupports*);
   static void SetStaticAttribute(nsISupports*, bool);
 
   // Miscellania
   int32_t AttrWithLenientThis();
   void SetAttrWithLenientThis(int32_t);
   uint32_t UnforgeableAttr();
   uint32_t UnforgeableAttr2();
+  void Stringify(nsString&);
   void PassRenamedInterface(nsRenamedInterface&);
   TestInterface* PutForwardsAttr();
   TestInterface* PutForwardsAttr2();
   TestInterface* PutForwardsAttr3();
 
   // Methods and properties imported via "implements"
   bool ImplementedProperty();
   void SetImplementedProperty(bool);

--- a/dom/bindings/test/TestCodeGen.webidl
+++ b/dom/bindings/test/TestCodeGen.webidl
@@ -337,16 +337,17 @@ interface TestInterface {
   // Static methods and attributes
   static attribute boolean staticAttribute;
   static void staticMethod(boolean arg);
 
   // Miscellania
   [LenientThis] attribute long attrWithLenientThis;
   [Unforgeable] readonly attribute long unforgeableAttr;
   [Unforgeable, ChromeOnly] readonly attribute long unforgeableAttr2;
+  stringifier;
   void passRenamedInterface(TestRenamedInterface arg);
   [PutForwards=writableByte] readonly attribute TestInterface putForwardsAttr;
   [PutForwards=writableByte, LenientThis] readonly attribute TestInterface putForwardsAttr2;
   [PutForwards=writableByte, ChromeOnly] readonly attribute TestInterface putForwardsAttr3;
 
   // If you add things here, add them to TestExampleGen as well
 };
 

--- a/dom/bindings/test/TestExampleGen.webidl
+++ b/dom/bindings/test/TestExampleGen.webidl
@@ -304,15 +304,16 @@ interface TestExampleInterface {
   // Static methods and attributes
   static attribute boolean staticAttribute;
   static void staticMethod(boolean arg);
 
   // Miscellania
   [LenientThis] attribute long attrWithLenientThis;
   [Unforgeable] readonly attribute long unforgeableAttr;
   [Unforgeable, ChromeOnly] readonly attribute long unforgeableAttr2;
+  stringifier;
   void passRenamedInterface(TestRenamedInterface arg);
   [PutForwards=writableByte] readonly attribute TestExampleInterface putForwardsAttr;
   [PutForwards=writableByte, LenientThis] readonly attribute TestExampleInterface putForwardsAttr2;
   [PutForwards=writableByte, ChromeOnly] readonly attribute TestExampleInterface putForwardsAttr3;
 
   // If you add things here, add them to TestCodeGen as well
 };