Per isolate package root.

runtime/bin/isolate_data.h

 // Copyright (c) 2012, 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.
 
 #ifndef BIN_ISOLATE_DATA_H_
 #define BIN_ISOLATE_DATA_H_
 
 #include "include/dart_api.h"
 #include "platform/globals.h"
 
 
 namespace dart {
 namespace bin {
 
 // Forward declaration.
 class EventHandler;
 
 // Data associated with every isolate in the standalone VM
 // embedding. This is used to free external resources for each isolate
 // when the isolate shuts down.
 class IsolateData {
  public:
-  explicit IsolateData(const char* url)
-      : script_url(strdup(url)), udp_receive_buffer(NULL) {
+  explicit IsolateData(const char* url, const char* package_root)
+      : script_url(strdup(url)),
+        package_root(NULL),
+        udp_receive_buffer(NULL) {
+    if (package_root != NULL) {
+      this->package_root = strdup(package_root);
+    }
   }
   ~IsolateData() {
     free(script_url);
+    free(package_root);
     free(udp_receive_buffer);
   }
 
   char* script_url;
+  char* package_root;
   uint8_t* udp_receive_buffer;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(IsolateData);
 };
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // BIN_ISOLATE_DATA_H_