Change mojo enums to be scoped enums in the generated C++ bindings.

mojo/public/interfaces/bindings/tests/test_structs.mojom

 // 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.
 
 [JavaPackage="org.chromium.mojo.bindings.test.mojom.test_structs"]
 module mojo.test;
 
 import "mojo/public/interfaces/bindings/tests/rect.mojom";
 
 struct NamedRegion {
@@ skipping 79 matching lines @@
 struct ScopedConstants {
   const int32 TEN = 10;
   const int32 ALSO_TEN = TEN;
   enum EType {
     E0,
     E1,
     E2 = 10,
     E3 = E2,
     E4,
   };
-  const int32 TEN_TOO = EType.E2;
   EType f0 = E0; // 0
   EType f1 = E1; // 1
   EType f2 = E2; // 10
   EType f3 = E3; // 10
   EType f4 = E4; // 11
   int32 f5 = TEN;
   int32 f6 = ALSO_TEN;
 };
 
 // Used to verify that all possible Map key field types can be encoded and
@@ skipping 257 matching lines @@
 
 struct ContainsOther {
   int32 other;
 };
 
 // Used to verify that structs can contain interface requests.
 
 struct ContainsInterfaceRequest {
   SomeInterface& request;
 };