Cleanups in the Mojo package.

mojo/dart/packages/mojo/lib/src/message_pipe.dart

Index: mojo/dart/packages/mojo/lib/src/message_pipe.dart
diff --git a/mojo/dart/packages/mojo/lib/src/message_pipe.dart b/mojo/dart/packages/mojo/lib/src/message_pipe.dart
index 7ecf10137393fa855e4f5c67f27b63d9af7f9b37..b638c4943e9fc9a7cb0bc236b91947afc57208f2 100644
--- a/mojo/dart/packages/mojo/lib/src/message_pipe.dart
+++ b/mojo/dart/packages/mojo/lib/src/message_pipe.dart
@@ -54,9 +54,9 @@ class MojoMessagePipeQueryAndReadState {
 }
 
 class MojoMessagePipeEndpoint {
-  static const int WRITE_FLAG_NONE = 0;
-  static const int READ_FLAG_NONE = 0;
-  static const int READ_FLAG_MAY_DISCARD = 1 << 0;
+  static const int WRITE_FLAG_NONE = MojoConstants.kNone;
+  static const int READ_FLAG_NONE = MojoConstants.kNone;
+  static const int READ_FLAG_MAY_DISCARD = MojoConstants.kMayDiscard;
 
   static final _queryAndReadState = new MojoMessagePipeQueryAndReadState();
 
@@ -177,14 +177,14 @@ class MojoMessagePipeEndpoint {
 }
 
 class MojoMessagePipe {
-  static const int FLAG_NONE = 0;
+  static const int flagNone = MojoConstants.kNone;
 
   List<MojoMessagePipeEndpoint> endpoints;
   int status;
 
   MojoMessagePipe._() : status = MojoResult.kOk;
 
-  factory MojoMessagePipe([int flags = FLAG_NONE]) {
+  factory MojoMessagePipe([int flags = flagNone]) {
     List result = MojoMessagePipeNatives.MojoCreateMessagePipe(flags);
     if (result == null) {
       return null;