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

mojo/public/cpp/bindings/tests/request_response_unittest.cc

Index: mojo/public/cpp/bindings/tests/request_response_unittest.cc
diff --git a/mojo/public/cpp/bindings/tests/request_response_unittest.cc b/mojo/public/cpp/bindings/tests/request_response_unittest.cc
index fa4ffa186960edfac85d6e396426170deb319a30..d0d97546c1245f67db42bfb12e2edc84a91ab1d5 100644
--- a/mojo/public/cpp/bindings/tests/request_response_unittest.cc
+++ b/mojo/public/cpp/bindings/tests/request_response_unittest.cc
@@ -143,11 +143,11 @@ TEST_F(RequestResponseTest, EchoEnum) {
   ProviderImpl provider_impl(GetProxy(&provider));
 
   sample::Enum value;
-  provider->EchoEnum(sample::ENUM_VALUE, EnumRecorder(&value));
+  provider->EchoEnum(sample::Enum::VALUE, EnumRecorder(&value));
 
   PumpMessages();
 
-  EXPECT_EQ(sample::ENUM_VALUE, value);
+  EXPECT_EQ(sample::Enum::VALUE, value);
 }
 
 }  // namespace