Rename blahHandler to onBlah throughout dart:io.

tests/standalone/src/ProcessWorkingDirectoryTest.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.
 //
 // Process working directory test.
 
 #library("ProcessWorkingDirectoryTest");
 #import("dart:io");
 #source("ProcessTestUtil.dart");
 
 class ProcessWorkingDirectoryTest {
   static String get fullTestFilePath() {
     // Extract full path, since we run processes from another directory.
     File path = new File(getProcessTestFileName());
     Expect.isTrue(path.existsSync());
     return path.fullPathSync();
   }
 
   static void testValidDirectory() {
     Directory directory = new Directory("");
     directory.createTempSync();
     Expect.isTrue(directory.existsSync());
 
     Process process = new Process.start(fullTestFilePath,
                                         const ["0", "0", "99", "0"],
                                         directory.path);
 
-    process.exitHandler = (int exitCode) {
+    process.onExit = (int exitCode) {
       Expect.equals(exitCode, 99);
       process.close();
       directory.deleteSync();
     };
 
-    process.errorHandler = (error) {
+    process.onError = (error) {
       Expect.fail("error running process $error");
       directory.deleteSync();
     };
   }
 
   static void testInvalidDirectory() {
     Directory directory = new Directory("");
     directory.createTempSync();
     Expect.isTrue(directory.existsSync());
 
     Process process = new Process.start(fullTestFilePath,
                                         const ["0", "0", "99", "0"],
                                         directory.path + "/subPath");
 
-    process.exitHandler = (int exitCode) {
+    process.onExit = (int exitCode) {
       Expect.fail("bad process completed");
       process.close();
       directory.deleteSync();
     };
 
-    process.errorHandler = (error) {
+    process.onError = (error) {
       Expect.isNotNull(error);
       directory.deleteSync();
     };
   }
 }
 
 
 
 main() {
   ProcessWorkingDirectoryTest.testValidDirectory();
   ProcessWorkingDirectoryTest.testInvalidDirectory();
 }