Support nullable attributes and return types in Dartium.

tools/dom/scripts/idlrenderer.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.
 
 from idlnode import *
 
 
 def render(idl_node, indent_str='  '):
   output = []
@@ skipping 123 matching lines @@
       if node.id:
         w(node.id)
       w('(')
       w(node.arguments, ', ')
       w(')')
     elif isinstance(node, IDLAttribute):
       wsp(node.annotations)
       wsp(node.ext_attrs)
       if node.is_read_only:
         w('readonly ')
-      w('attribute %s %s' % (node.type.id, node.id))
+      w('attribute ')
+      w(node.type.id)
+      if (node.type.nullable):
+        w('?')
+      w(' ')
+      w(node.id)
       if node.raises:
         w(' raises (%s)' % node.raises.id)
       else:
         if node.get_raises:
           w(' getraises (%s)' % node.get_raises.id)
         if node.set_raises:
           w(' setraises (%s)' % node.set_raises.id)
       wln(';')
     elif isinstance(node, IDLConstant):
       wsp(node.annotations)
       wsp(node.ext_attrs)
       wln('const %s %s = %s;' % (node.type.id, node.id, node.value))
     elif isinstance(node, IDLOperation):
       wsp(node.annotations)
       wsp(node.ext_attrs)
       if node.is_static:
         w('static ')
       if node.specials:
         w(node.specials, ' ')
         w(' ')
-      w('%s ' % node.type.id)
+      w(node.type.id)
+      if (node.type.nullable):
+        w('?')
+      w(' ')
       w(node.id)
       w('(')
       w(node.arguments, ', ')
       w(')')
       if node.raises:
         w(' raises (%s)' % node.raises.id)
       wln(';')
     elif isinstance(node, IDLArgument):
       wsp(node.ext_attrs)
       w('in ')
       w('%s %s' % (node.type.id, node.id))
     else:
       raise TypeError("Expected str or IDLNode but %s found" %
         type(node))
 
   w(idl_node)
   return ''.join(output)