Move more Mojo bindings helpers out of internal namespace

mojo/public/cpp/bindings/lib/message_internal.h

Index: mojo/public/cpp/bindings/lib/message_internal.h
diff --git a/mojo/public/cpp/bindings/lib/message_internal.h b/mojo/public/cpp/bindings/lib/message_internal.h
index b4fd3347ee9c308d53d791a1ecee256fafe9ff21..63edffd7cbdbfff7be3b76cde15e42602c541737 100644
--- a/mojo/public/cpp/bindings/lib/message_internal.h
+++ b/mojo/public/cpp/bindings/lib/message_internal.h
@@ -14,12 +14,6 @@ namespace internal {
 
 #pragma pack(push, 1)
 
-enum {
-  kMessageExpectsResponse = 1 << 0,
-  kMessageIsResponse = 1 << 1,
-  kMessageIsSync = 1 << 2
-};
-
 struct MessageHeader : internal::StructHeader {
   // Interface ID for identifying multiple interfaces running on the same
   // message pipe.
@@ -34,7 +28,7 @@ struct MessageHeader : internal::StructHeader {
 static_assert(sizeof(MessageHeader) == 24, "Bad sizeof(MessageHeader)");
 
 struct MessageHeaderWithRequestID : MessageHeader {
-  // Only used if either kMessageExpectsResponse or kMessageIsResponse is set in
+  // Only used if either kFlagExpectsResponse or kFlagIsResponse is set in
   // order to match responses with corresponding requests.
   uint64_t request_id;
 };