Fix updating packages map on reload and add a regression test

runtime/bin/loader.cc

 // Copyright (c) 2016, 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.
 
 
 #include "bin/loader.h"
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
 #include "bin/extensions.h"
@@ skipping 634 matching lines @@
     }
     Dart_Handle library_url = Dart_LibraryUrl(library);
     if (Dart_IsError(library_url)) {
       return library_url;
     }
   }
 
   IsolateData* isolate_data =
       reinterpret_cast<IsolateData*>(Dart_CurrentIsolateData());
   ASSERT(isolate_data != NULL);
-
+  if ((tag == Dart_kScriptTag) && Dart_IsString(library)) {
+    // Update packages file for isolate.
+    const char* packages_file = NULL;
+    Dart_Handle result = Dart_StringToCString(library, &packages_file);
+    if (Dart_IsError(result)) {
+      return result;
+    }
+    isolate_data->UpdatePackagesFile(packages_file);
+  }
   // Grab this isolate's loader.
   Loader* loader = NULL;
 
   // The outer invocation of the tag handler for this isolate. We make the outer
   // invocation block and allow any nested invocations to operate in parallel.
   const bool blocking_call = !isolate_data->HasLoader();
 
   // If we are the outer invocation of the tag handler and the tag is an import
   // this means that we are starting a deferred library load.
   const bool is_deferred_import = blocking_call && (tag == Dart_kImportTag);
@@ skipping 197 matching lines @@
   MutexLocker ml(loader_infos_lock_);
   Loader* loader = LoaderForLocked(dest_port_id);
   if (loader == NULL) {
     return;
   }
   loader->QueueMessage(message);
 }
 
 }  // namespace bin
 }  // namespace dart