Change dart:io Platform.script to return a Uri.

tests/standalone/debugger/debug_lib.dart

 // Copyright (c) 2013, 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.
 
 // Library used by debugger wire protocol tests (standalone VM debugging).
 
 library DartDebugger;
 
 import "dart:async";
 import "dart:convert";
@@ skipping 589 matching lines @@
 
 
 bool RunScript(List script, List<String> arguments) {
   if (arguments.contains("--debuggee")) {
     return false;
   }
   verboseWire = arguments.contains("--wire");
 
   // Port number 0 means debug target picks a free port dynamically.
   var targetOpts = [ "--debug:0" ];
-  targetOpts.add(Platform.script);
+  targetOpts.add(Platform.script.toFilePath());
   targetOpts.add("--debuggee");
   print('args: ${targetOpts.join(" ")}');
 
   Process.start(Platform.executable, targetOpts).then((Process process) {
     print("Debug target process started, pid ${process.pid}.");
     process.stdin.close();
     var debugger = new Debugger(process, new DebugScript(script));
   });
   return true;
 }