Dart: Renames dart:mojo_blah -> mojo:blah

mojo/dart/embedder/test/dart_to_cpp_tests.dart

 // Copyright 2014 The Chromium Authors. 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:async';
-import 'dart:mojo_bindings' as bindings;
-import 'dart:mojo_core' as core;
 import 'dart:typed_data';
+import 'mojo:bindings' as bindings;
+import 'mojo:core' as core;
 
 import 'package:mojo/dart/embedder/test/dart_to_cpp.mojom.dart';
 
 class DartSideImpl extends DartSide {
   static const int BAD_VALUE = 13;
   static const int ELEMENT_BYTES = 1;
   static const int CAPACITY_BYTES = 64;
 
   CppSideProxy cppSide;
 
@@ skipping 92 matching lines @@
   assert(args.length == 2);
   int mojoHandle = args[0];
   var rawHandle = new core.MojoHandle(mojoHandle);
   var endpoint = new core.MojoMessagePipeEndpoint(rawHandle);
   var dartSide = new DartSideImpl(endpoint);
   dartSide.listen();
   dartSide.future.then((_) {
     print('Success');
   });
 }