Reverts change to debug_lib.dart

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 576 matching lines @@
     // If the process was already dead exitCode is already
     // available and we call exit() in the next event loop cycle.
     // Otherwise this will wait for the process to exit.
     targetProcess.exitCode.then((exitCode) {
       print("process $targetPid terminated with exit code $exitCode.");
       if (errorsDetected) {
         print("\n===== Errors detected: =====");
         for (int i = 0; i < errors.length; i++) print(errors[i]);
         print("============================\n");
       }
-      exit(exitCode);
+      exit(errors.length);
     });
     cleanupDone = true;
   }
 }
 
 
 bool RunScript(List script) {
   var options = new Options();
   if (options.arguments.contains("--debuggee")) {
     return false;
   }
   verboseWire = options.arguments.contains("--wire");
 
   // Port number 0 means debug target picks a free port dynamically.
   var targetOpts = [ "--debug:0" ];
   targetOpts.add(Platform.script);
   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;
 }