DevTools: use target-based model accessors only.

Source/devtools/front_end/sdk/RuntimeModel.js

 /*
  * Copyright (C) 2012 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 448 matching lines @@
             if (prefix.length && !property.startsWith(prefix))
                 continue;
 
             results.push(property);
         }
         completionsReadyCallback(results);
     },
 
     __proto__: WebInspector.SDKObject.prototype
 }
-
-/**
- * @type {!WebInspector.RuntimeModel}
- */
-WebInspector.runtimeModel;