Use WebKit IDL syntax for declaring optional parameters in dart.idl.

lib/dom/scripts/idlnode.py

 #!/usr/bin/python
 # Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 import sys
 
 
 class IDLNode(object):
   """Base class for all IDL elements.
@@ skipping 441 matching lines @@
     IDLMember.__init__(self, ast, doc_js_interface_name)
     self.value = self._find_first(ast, 'ConstExpr')
 
 
 class IDLArgument(IDLNode):
   """IDLNode specialization for operation arguments."""
   def __init__(self, ast):
     IDLNode.__init__(self, ast)
     self.type = self._convert_first(ast, 'Type', IDLType)
     self._convert_ext_attrs(ast)
-    # WebKit and Web IDL differ in how Optional is declared:
-    self.is_optional = self._has(ast, 'Optional') \
-      or ('Optional' in self.ext_attrs)
+    self.is_optional = 'Optional' in self.ext_attrs
 
   def __repr__(self):
     return '<IDLArgument(type = %s, id = %s)>' % (self.type, self.id)
 
 
 class IDLImplementsStatement(IDLNode):
   """IDLNode specialization for 'X implements Y' declarations."""
   def __init__(self, ast):
     IDLNode.__init__(self, ast)
     self.implementor = self._convert_first(ast, 'ImplStmtImplementor',
@@ skipping 19 matching lines @@
   """IDLDictNode specialization for one annotation."""
   def __init__(self, ast=None):
     IDLDictNode.__init__(self, ast)
     self.id = None
     if not ast:
       return
     for arg in self._find_all(ast, 'AnnotationArg'):
       name = self._find_first(arg, 'Id')
       value = self._find_first(arg, 'AnnotationArgValue')
       self[name] = value