Reapply r3590 with frog fixes

client/dom/scripts/dartgenerator.py

Index: client/dom/scripts/dartgenerator.py
diff --git a/client/dom/scripts/dartgenerator.py b/client/dom/scripts/dartgenerator.py
index 98021ad1b6e0bc89b8a92b37e483a52a15212552..0a8184d4cacfab2ba85606a4f436a565665394fd 100755
--- a/client/dom/scripts/dartgenerator.py
+++ b/client/dom/scripts/dartgenerator.py
@@ -725,14 +725,21 @@ class OperationInfo(object):
     return ', '.join(argtexts)
 
 
+def MaybeListElementTypeName(type_name):
+  """Returns the List element type T from string of form "List<T>", or None."""
+  match = re.match(r'List<(\w*)>$', type_name)
+  if match:
+    return match.group(1)
+  return None
+
 def MaybeListElementType(interface):
   """Returns the List element type T, or None in interface does not implement
   List<T>.
   """
   for parent in interface.parents:
-    match = re.match(r'List<(\w*)>$', parent.type.id)
-    if match:
-      return match.group(1)
+    element_type = MaybeListElementTypeName(parent.type.id)
+    if element_type:
+      return element_type
   return None
 
 def MaybeTypedArrayElementType(interface):
@@ -1857,6 +1864,7 @@ class FrogInterfaceGenerator(object):
     if base:
       extends = ' extends ' + base
     elif native_spec[0] == '=':
+      # The implementation is a singleton with no prototype.
       extends = ''
     else:
       extends = ' extends DOMTypeJs'
@@ -1976,13 +1984,13 @@ class FrogInterfaceGenerator(object):
     #
     self._members_emitter.Emit(
         '\n'
-        '  $TYPE operator[](int index) native;\n',
+        '  $TYPE operator[](int index) native "return this[index];";\n',
         TYPE=self._NarrowOutputType(element_type))
 
     if 'HasCustomIndexSetter' in self._interface.ext_attrs:
       self._members_emitter.Emit(
           '\n'
-          '  void operator[]=(int index, $TYPE value) native;\n',
+          '  void operator[]=(int index, $TYPE value) native "this[index] = value";\n',
           TYPE=self._NarrowInputType(element_type))
     else:
       self._members_emitter.Emit(
@@ -1992,6 +2000,12 @@ class FrogInterfaceGenerator(object):
           '  }\n',
           TYPE=self._NarrowInputType(element_type))
 
+    # TODO(sra): Use separate mixins for mutable implementations of List<T>.
+    # TODO(sra): Use separate mixins for typed array implementations of List<T>.
+    template_file = 'immutable_list_mixin.darttemplate'
+    template = self._system._templates.Load(template_file)
+    self._members_emitter.Emit(template, E=element_type)
+
 
   def AddTypedArrayConstructors(self, element_type):
     self._members_emitter.Emit(