Rename blahHandler to onBlah throughout dart:io.

tests/standalone/src/ChunkedStreamTest.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #import("dart:io");
 #import("dart:isolate");
 
 void test1() {
   void testWithChunkSize(var data, int chunkSize, Function testDone) {
     InputStream list_input_stream = new ListInputStream();
@@ skipping 20 matching lines @@
         }
         chunkCount++;
       }
     }
 
     void closeHandler() {
       Expect.equals(data.length, byteCount);
       testDone(byteCount);
     }
 
-    stream.dataHandler = chunkData;
-    stream.closeHandler = closeHandler;
+    stream.onData = chunkData;
+    stream.onClosed = closeHandler;
     stream.chunkSize = chunkSize;
   }
 
   for (int i = 1; i <= 10; i++) {
     var data = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
 
     void testDone(int byteCount) {
       Expect.equals(data.length, byteCount);
     }
 
@@ skipping 64 matching lines @@
       Expect.equals(null, chunk);
       stage++;
       donePort.toSendPort().send(stage);
     }
   }
 
   void streamClosed() {
     Expect.equals(5, stage);
   }
 
-  stream.dataHandler = chunkData;
-  stream.closeHandler = streamClosed;
+  stream.onData = chunkData;
+  stream.onClosed = streamClosed;
   s.write([0, 1, 2, 3]);  // 4 bytes written to stream.
   Expect.equals(0, stage);
   s.write([4, 5, 6]);  // 7 bytes written to stream.
 
   donePort.receive((x,y) => donePort.close());
 }
 
 
 main() {
   test1();
   test2();
 }