IDL: Support 'stringifier' keyword

Source/bindings/tests/idls/TestObject.idl

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 49 matching lines @@
     const unsigned short CONST_VALUE_15 = 010;
     const unsigned short CONST_VALUE_16 = -010;
     const unsigned short CONST_VALUE_16 = -0x1A;
     const unsigned short CONST_VALUE_17 = -0X1a;
 
     // Extended attributes
     [DeprecateAs=Constant] const short DEPRECATED_CONSTANT = 1;
     [RuntimeEnabled=FeatureName] const short FEATURE_ENABLED_CONST = 1;
     [Reflect=CONST_IMPL] const short CONST_JAVASCRIPT = 1;
 
+    stringifier attribute DOMString stringifierAttribute;
 
     // Attributes
     //
     // Naming convention:
     // [ExtAttr] attribute Type extAttrTypeNameAttribute;
     // E.g.,
     // [Foo] attribute DOMString? fooStringOrNullAttribute
     //
     // Type name reference:
     // http://heycam.github.io/webidl/#dfn-type-name
@@ skipping 439 matching lines @@
     void voidMethodTestInterfaceWillBeGarbageCollectedArrayArg(TestInterfaceWillBeGarbageCollected[] testInterfaceWillBeGarbageCollectedArrayArg);
 
     // Extended attributes on referenced interfaces
     // (not self; self-reference tests at interface themselves)
     attribute TestInterface testInterfaceAttribute; // [ImplementedAs]
     attribute TestInterfaceGarbageCollected testInterfaceGarbageCollectedAttribute; // [GarbageCollected]
     attribute TestInterfaceGarbageCollected? testInterfaceGarbageCollectedOrNullAttribute; // [GarbageCollected]
     attribute TestInterfaceWillBeGarbageCollected testInterfaceWillBeGarbageCollectedAttribute; // [WillBeGarbageCollected]
     attribute TestInterfaceWillBeGarbageCollected? testInterfaceWillBeGarbageCollectedOrNullAttribute; // [WillBeGarbageCollected]
 };