For c++, Generate enum classes instead of enum from mojom.

examples/http_handler/http_handler.cc

Index: examples/http_handler/http_handler.cc
diff --git a/examples/http_handler/http_handler.cc b/examples/http_handler/http_handler.cc
index 365ee3e8a82b8db3719bd600f642bc4ebe975764..bf6b39e80715901f6a90fafee81b781a22e7a420 100644
--- a/examples/http_handler/http_handler.cc
+++ b/examples/http_handler/http_handler.cc
@@ -36,7 +36,7 @@ class HttpHandler : public ApplicationDelegate,
     app->ConnectToService("mojo:http_server", &http_server_factory);
 
     mojo::NetAddressPtr local_address(mojo::NetAddress::New());
-    local_address->family = mojo::NET_ADDRESS_FAMILY_IPV4;
+    local_address->family = mojo::NetAddressFamily::IPV4;
     local_address->ipv4 = mojo::NetAddressIPv4::New();
     local_address->ipv4->addr.resize(4);
     local_address->ipv4->addr[0] = 0;