Mojo C++ bindings: support setting default value for fields whose types are typemapped enums.

mojo/public/tools/bindings/generators/mojom_cpp_generator.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.
 
 """Generates C++ source files from a mojom.Module."""
 
 import mojom.generate.generator as generator
 import mojom.generate.module as mojom
 import mojom.generate.pack as pack
 from mojom.generate.template_expander import UseJinja
@@ skipping 382 matching lines @@
     else:
       suffix = "-%s" % self.variant if self.variant else ""
       self.Write(self._GenerateModuleHeader(),
                  "%s%s.h" % (self.module.path, suffix))
       self.Write(self._GenerateModuleSource(),
                  "%s%s.cc" % (self.module.path, suffix))
 
   def _ConstantValue(self, constant):
     return self._ExpressionToText(constant.value, kind=constant.kind)
 
-  # TODO(yzshen): Revisit the default value feature. It was designed prior to
-  # custom type mapping.
   def _DefaultValue(self, field):
-    if field.default:
-      if mojom.IsStructKind(field.kind):
-        assert field.default == "default"
-        if not self._IsTypemappedKind(field.kind):
-          return "%s::New()" % self._GetNameForKind(field.kind)
-      return self._ExpressionToText(field.default, kind=field.kind)
-    return ""
+    if not field.default:
+      return ""
+
+    if mojom.IsStructKind(field.kind):
+      assert field.default == "default"
+      if self._IsTypemappedKind(field.kind):
+        return ""
+      return "%s::New()" % self._GetNameForKind(field.kind)
+
+    expression = self._ExpressionToText(field.default, kind=field.kind)
+    if mojom.IsEnumKind(field.kind) and self._IsTypemappedKind(field.kind):
+      expression = "mojo::internal::ConvertEnumValue<%s, %s>(%s)" % (
+          self._GetNameForKind(field.kind), self._GetCppWrapperType(field.kind),
+          expression)
+    return expression
 
   def _GetNameForKind(self, kind, internal=False, flatten_nested_kind=False,
                       add_same_module_namespaces=False):
     return _NameFormatter(kind, self.variant).FormatForCpp(
         internal=internal, flatten_nested_kind=flatten_nested_kind,
         omit_namespace_for_module = (None if add_same_module_namespaces
                                           else self.module))
 
   def _GetQualifiedNameForKind(self, kind, internal=False,
                                flatten_nested_kind=False, include_variant=True):
@@ skipping 372 matching lines @@
     if mojom.IsDataPipeProducerKind(kind):
       return "mojo::ScopedDataPipeProducerHandle"
     if mojom.IsMessagePipeKind(kind):
       return "mojo::ScopedMessagePipeHandle"
     if mojom.IsSharedBufferKind(kind):
       return "mojo::ScopedSharedBufferHandle"
     return _kind_to_cpp_type[kind]
 
   def _GetUnmappedTypeForSerializer(self, kind):
     return self._GetCppDataViewType(kind, qualified=True)