VM: Fix snapshoting slow-down caused by 99c6a18a1bc2a4f13d8dd027a597fdca0f2d6e0c.

runtime/bin/vmservice/loader.dart

 // Copyright (c) 2015, 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.
 
 part of vmservice_io;
 
 _sanitizeWindowsPath(path) {
   // For Windows we need to massage the paths a bit according to
   // http://blogs.msdn.com/b/ie/archive/2006/12/06/file-uris-in-windows.aspx
   //
@@ skipping 1017 matching lines @@
         _handleResourceRequest(
             loaderState, sp, traceLoading, tag, uri, uri, libraryUrl);
       }
       break;
     case _Dart_kInitLoader:
       {
         String packageRoot = request[4];
         String packagesFile = request[5];
         String workingDirectory = request[6];
         String rootScript = request[7];
+        bool isReloading = request[8];
         if (loaderState == null) {
           loaderState = new IsolateLoaderState(isolateId);
           isolateEmbedderData[isolateId] = loaderState;
           loaderState.init(
               packageRoot, packagesFile, workingDirectory, rootScript);
-        } else {
+        } else if (isReloading) {
           loaderState.updatePackageMap(packagesFile);
         }
         loaderState.sp = sp;
         assert(isolateEmbedderData[isolateId] == loaderState);
       }
       break;
     case _Dart_kResourceLoad:
       {
         Uri uri = Uri.parse(request[4]);
         _handleResourceRequest(
@@ skipping 105 matching lines @@
           msg[3] = null;
           msg[4] = e.toString();
           sp.send(msg);
         }
       });
       break;
     default:
       _log('Unknown loader request tag=$tag from $isolateId');
   }
 }