Initialize content scripts the same way extension scripts are.

chrome/renderer/resources/event_bindings.js

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 var chrome = chrome || {};
 (function () {
   native function GetChromeHidden();
   native function AttachEvent(eventName);
   native function DetachEvent(eventName);
   native function GetExternalFileEntry(fileDefinition);
@@ skipping 214 matching lines @@
     this.validate_ = [];
     this.detach_();
   };
 
   // Special load events: we don't use the DOM unload because that slows
   // down tab shutdown.  On the other hand, onUnload might not always fire,
   // since Chrome will terminate renderers on shutdown (SuddenTermination).
   chromeHidden.onLoad = new chrome.Event();
   chromeHidden.onUnload = new chrome.Event();
 
-  chromeHidden.dispatchOnLoad = function(extensionId) {
-    chromeHidden.onLoad.dispatch(extensionId);
+  chromeHidden.dispatchOnLoad = function(extensionId, isExtensionProcess,
+                                         isIncognitoContext) {
+    chromeHidden.onLoad.dispatch(extensionId, isExtensionProcess,
+                                 isIncognitoContext);
   };
 
   chromeHidden.dispatchOnUnload = function() {
     chromeHidden.onUnload.dispatch();
     for (var i = 0; i < allAttachedEvents.length; ++i) {
       var event = allAttachedEvents[i];
       if (event)
         event.detach_();
     }
   };
 
   chromeHidden.dispatchError = function(msg) {
     console.error(msg);
   };
 })();