Dart: Merge message pipe query and read into one native call.

mojo/public/dart/mojo/lib/src/stub.dart

Index: mojo/public/dart/mojo/lib/src/stub.dart
diff --git a/mojo/public/dart/mojo/lib/src/stub.dart b/mojo/public/dart/mojo/lib/src/stub.dart
index 4957dd9702a7a737e1266837a4ba326466368d04..7ea00593e1f318f7a5b8e9899e5e6482831f0eaf 100644
--- a/mojo/public/dart/mojo/lib/src/stub.dart
+++ b/mojo/public/dart/mojo/lib/src/stub.dart
@@ -19,27 +19,22 @@ abstract class Stub extends core.MojoEventStreamListener {
   dynamic handleMessage(ServiceMessage message);
 
   void handleRead() {
-    // Query how many bytes are available.
-    var result = endpoint.query();
-    assert(result.status.isOk || result.status.isResourceExhausted);
-    if (result.bytesRead == 0) {
-      throw new MojoCodecError('Unexpected empty message: $this');
+    var result = endpoint.queryAndRead();
+    if ((result.bytesRead == null) || (result.bytesRead.length == 0)) {
+      throw new MojoCodecError('Unexpected empty message or error: $result');
     }
 
-    // Read the data and view as a message.
-    var bytes = new ByteData(result.bytesRead);
-    var handles = new List<core.MojoHandle>(result.handlesRead);
-    result = endpoint.read(bytes, result.bytesRead, handles);
-    assert(result.status.isOk || result.status.isResourceExhausted);
-
     // Prepare the response.
     var message;
     var response;
     try {
-      message = new ServiceMessage.fromMessage(new Message(bytes, handles));
+      message = new ServiceMessage.fromMessage(
+          new Message(result.bytesRead, result.handlesRead));
       response = _isClosing ? null : handleMessage(message);
     } catch (e) {
-      handles.forEach((h) => h.close());
+      if (result.handlesRead != null) {
+        result.handlesRead.forEach((h) => h.close());
+      }
       rethrow;
     }