[mojo-bindings] Support reuse of native enum classes

mojo/public/tools/bindings/pylib/mojom/generate/data.py

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # TODO(vtl): "data" is a pretty vague name. Rename it?
 
 import copy
 
 import module as mojom
 
@@ skipping 379 matching lines @@
       prev_value = resolved_enum_values[field.value.name]
     else:
       raise Exception("Unresolved enum value.")
 
     resolved_enum_values[field.name] = prev_value
     field.numeric_value = prev_value
 
 def EnumFromData(module, data, parent_kind):
   enum = mojom.Enum(module=module)
   enum.name = data['name']
+  enum.native_only = data['native_only']
   name = enum.name
   if parent_kind:
     name = parent_kind.name + '.' + name
   enum.spec = 'x:%s.%s' % (module.namespace, name)
   enum.parent_kind = parent_kind
   enum.fields = map(
       lambda field: EnumFieldFromData(module, enum, field, parent_kind),
-      data['fields'])
+      data['fields']) if not enum.native_only else []
   enum.attributes = data.get('attributes')
   ResolveNumericEnumValues(enum.fields)
 
   module.kinds[enum.spec] = enum
+
+  # Enforce that a [native=True] attribute is set to make native-only enum
+  # declarations more explicit.
+  if enum.native_only:
+    if not enum.attributes or not enum.attributes.get('native', False):
+      raise Exception("Native-only enum declarations must include a " +
+                      "native=True attribute.")
   return enum
 
 def ConstantFromData(module, data, parent_kind):
   constant = mojom.Constant()
   constant.name = data['name']
   if parent_kind:
     scope = (module.namespace, parent_kind.name)
   else:
     scope = (module.namespace, )
   # TODO(mpcomplete): maybe we should only support POD kinds.
@@ skipping 71 matching lines @@
 
 def OrderedModuleFromData(data):
   module = ModuleFromData(data)
   for interface in module.interfaces:
     next_ordinal = 0
     for method in interface.methods:
       if method.ordinal is None:
         method.ordinal = next_ordinal
       next_ordinal = method.ordinal + 1
   return module