Some more removals of dart:utf.

utils/lib/file_system_vm.dart

Index: utils/lib/file_system_vm.dart
diff --git a/utils/lib/file_system_vm.dart b/utils/lib/file_system_vm.dart
index d84d08148c9bc6332945d278f19215b91a300949..99b936f18afcb1ab500babf3875106501a93a7ea 100644
--- a/utils/lib/file_system_vm.dart
+++ b/utils/lib/file_system_vm.dart
@@ -5,9 +5,9 @@
 // TODO(terry): Investigate common library for file I/O shared between frog and tools.
 
 library file_system_vm;
+import 'dart:convert';
 import 'dart:io';
 import 'file_system.dart';
-import 'dart:utf';
 
 /** File system implementation using the vm api's. */
 class VMFileSystem implements FileSystem {
@@ -23,7 +23,7 @@ class VMFileSystem implements FileSystem {
     var buffer = new List<int>(length);
     var bytes = file.readIntoSync(buffer, 0, length);
     file.closeSync();
-    return new String.fromCharCodes(new Utf8Decoder(buffer).decodeRest());
+    return UTF8.decode(bytes);
   }
 
   bool fileExists(String filename) {