Initialize content scripts the same way extension scripts are.

chrome/renderer/extensions/user_script_idle_scheduler.cc

 // 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.
 
 #include "chrome/renderer/extensions/user_script_idle_scheduler.h"
 
 #include "base/message_loop.h"
 #include "chrome/common/extensions/extension_error_utils.h"
 #include "chrome/common/extensions/extension_messages.h"
 #include "chrome/renderer/extensions/extension_dispatcher.h"
@@ skipping 128 matching lines @@
           return;
         }
       }
 
       WebScriptSource source(WebString::fromUTF8(params.code));
       if (params.in_main_world) {
         frame->executeScript(source);
       } else {
         std::vector<WebScriptSource> sources;
         sources.push_back(source);
-        UserScriptSlave::InsertInitExtensionCode(&sources, params.extension_id);
         frame->executeScriptInIsolatedWorld(
             extension_dispatcher_->user_script_slave()->
                 GetIsolatedWorldIdForExtension(extension, frame),
             &sources.front(), sources.size(), EXTENSION_GROUP_CONTENT_SCRIPTS);
       }
     } else {
       frame->document().insertUserStyleSheet(
           WebString::fromUTF8(params.code),
           // Author level is consistent with WebView::addUserStyleSheet.
           WebDocument::UserStyleAuthorLevel);
@@ skipping 10 matching lines @@
   if (!parent_frame)
     return false;
 
   for (WebFrame* child_frame = parent_frame->firstChild(); child_frame;
        child_frame = child_frame->nextSibling()) {
     frames_vector->push_back(child_frame);
     GetAllChildFrames(child_frame, frames_vector);
   }
   return true;
 }