Attempt 2 -- Fix updating packages map on reload and add a regression test

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 72 matching lines @@
       _rootScript = Uri.parse(rootScript);
     }
     // If the --package-root flag was passed.
     if (packageRootFlag != null) {
       _setPackageRoot(packageRootFlag);
     }
     // If the --packages flag was passed.
     if (packagesConfigFlag != null) {
       _setPackagesConfig(packagesConfigFlag);
     }
-    if (_fileRequestQueue == null) {
-      _fileRequestQueue = new List<FileRequest>();
-    }
+  }
+
+  void updatePackageMap(String packagesConfigFlag) {
+    _packageMap = null;
+    _setPackagesConfig(packagesConfigFlag);
   }
 
   void cleanup() {
     _dead = true;
     if (_packagesPort != null) {
       _packagesPort.close();
       _packagesPort = null;
     }
   }
 
@@ skipping 21 matching lines @@
 
   // The map describing how certain package names are mapped to Uris.
   Uri _packageConfig = null;
   Map<String, Uri> _packageMap = null;
 
   // We issue only 16 concurrent calls to File.readAsBytes() to stay within
   // platform-specific resource limits (e.g. max open files). The rest go on
   // _fileRequestQueue and are processed when we can safely issue them.
   static const int _maxFileRequests = 16;
   int currentFileRequests = 0;
-  List<FileRequest> _fileRequestQueue;
+  final List<FileRequest> _fileRequestQueue = new List<FileRequest>();
 
   bool get shouldIssueFileRequest => currentFileRequests < _maxFileRequests;
   void enqueueFileRequest(FileRequest fr) {
     _fileRequestQueue.add(fr);
   }
 
   FileRequest dequeueFileRequest() {
     if (_fileRequestQueue.length == 0) {
       return null;
     }
@@ skipping 879 matching lines @@
     case _Dart_kInitLoader:
       {
         String packageRoot = request[4];
         String packagesFile = request[5];
         String workingDirectory = request[6];
         String rootScript = request[7];
         if (loaderState == null) {
           loaderState = new IsolateLoaderState(isolateId);
           isolateEmbedderData[isolateId] = loaderState;
           loaderState.init(
-              packageRoot, packagesFile, workingDirectory, rootScript);
+            packageRoot, packagesFile, workingDirectory, rootScript);
+        } else {
+          loaderState.updatePackageMap(packagesFile);
         }
         loaderState.sp = sp;
         assert(isolateEmbedderData[isolateId] == loaderState);
       }
       break;
     case _Dart_kResourceLoad:
       {
         Uri uri = Uri.parse(request[4]);
         _handleResourceRequest(
             loaderState, sp, traceLoading, tag, uri, uri, null);
@@ skipping 102 matching lines @@
         msg[2] = resolvedUri.toString();
         msg[3] = null;
         msg[4] = e.toString();
         sp.send(msg);
       }
       break;
     default:
       _log('Unknown loader request tag=$tag from $isolateId');
   }
 }