Model each Dart library as its own ScriptState when devtools are enabled.

Source/core/inspector/InjectedScriptSource.js

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 235 matching lines @@
         }
         return objectId;
     },
 
     /**
      * @param {string} objectId
      * @return {Object}
      */
     _parseObjectId: function(objectId)
     {
-        return InjectedScriptHost.evaluate("(" + objectId + ")");
+        // FIXME: upstream the change from InjectedScriptHost.evaluate to JSON.parse.
+        return /** @type {Object} */ (JSON.parse(objectId));
     },
 
     /**
      * @param {string} objectGroupName
      */
     releaseObjectGroup: function(objectGroupName)
     {
         var group = this._objectGroups[objectGroupName];
         if (!group)
             return;
@@ skipping 1143 matching lines @@
      */
     _logEvent: function(event)
     {
         inspectedWindow.console.log(event.type, event);
     }
 }
 
 injectedScript._commandLineAPIImpl = new CommandLineAPIImpl();
 return injectedScript;
 })