Dart: Avoid MojoResult and MojoHandleSignals constructors.

mojo/dart/packages/mojo/lib/src/drain_data.dart

Index: mojo/dart/packages/mojo/lib/src/drain_data.dart
diff --git a/mojo/dart/packages/mojo/lib/src/drain_data.dart b/mojo/dart/packages/mojo/lib/src/drain_data.dart
index dc630bfbdc7c1a2fc73b72023bcebd4af8a2fe6a..380d84e6f60e5eb7efdfb7e8f86d2df065b8949c 100644
--- a/mojo/dart/packages/mojo/lib/src/drain_data.dart
+++ b/mojo/dart/packages/mojo/lib/src/drain_data.dart
@@ -19,10 +19,10 @@ class DataPipeDrainer {
   ByteData _copy(ByteData byteData) => new ByteData.view(
       new Uint8List.fromList(byteData.buffer.asUint8List()).buffer);
 
-  MojoResult _doRead() {
+  int _doRead() {
     ByteData thisRead = _consumer.beginRead();
     if (thisRead == null) {
-      throw 'Data pipe beginRead failed: ${_consumer.status}';
+      throw 'Data pipe beginRead failed: ${_consumer}';
     }
     _dataList.add(_copy(thisRead));
     _dataSize += thisRead.lengthInBytes;
@@ -44,22 +44,23 @@ class DataPipeDrainer {
   Future<ByteData> drain() {
     var completer = new Completer();
     _eventSubscription.subscribe((List<int> event) {
-      var mojoSignals = new MojoHandleSignals(event[1]);
-      if (mojoSignals.isReadable) {
-        var result = _doRead();
-        if (!result.isOk) {
+      int mojoSignals = event[1];
+      if (MojoHandleSignals.isReadable(mojoSignals)) {
+        int result = _doRead();
+        if (result != MojoResult.kOk) {
           _eventSubscription.close();
           _eventSubscription = null;
           completer.complete(_concatData());
         } else {
           _eventSubscription.enableReadEvents();
         }
-      } else if (mojoSignals.isPeerClosed) {
+      } else if (MojoHandleSignals.isPeerClosed(mojoSignals)) {
         _eventSubscription.close();
         _eventSubscription = null;
         completer.complete(_concatData());
       } else {
-        throw 'Unexpected handle event: $mojoSignals';
+        String signals = MojoHandleSignals.string(mojoSignals);
+        throw 'Unexpected handle event: $signals';
       }
     });
     return completer.future;