Move most of the remaining users of WebContentsObserver::tab_contents() to use web_contents().

chrome/browser/extensions/extension_tabs_module.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/browser/extensions/extension_tabs_module.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "base/base64.h"
@@ skipping 1612 matching lines @@
     // Delay the callback invocation until after the current JS call has
     // returned.
     MessageLoop::current()->PostTask(FROM_HERE, base::Bind(
         &DetectTabLanguageFunction::GotLanguage, this,
         helper->language_state().original_language()));
     return true;
   }
   // The tab contents does not know its language yet.  Let's  wait until it
   // receives it, or until the tab is closed/navigates to some other page.
   registrar_.Add(this, chrome::NOTIFICATION_TAB_LANGUAGE_DETERMINED,
-                 content::Source<TabContents>(contents->tab_contents()));
+                 content::Source<WebContents>(contents->tab_contents()));
   registrar_.Add(
       this, content::NOTIFICATION_TAB_CLOSING,
       content::Source<NavigationController>(
           &(contents->tab_contents()->GetController())));
   registrar_.Add(
       this, content::NOTIFICATION_NAV_ENTRY_COMMITTED,
       content::Source<NavigationController>(
           &(contents->tab_contents()->GetController())));
   return true;
 }
@@ skipping 12 matching lines @@
   // called for every API call the extension made.
   GotLanguage(language);
 }
 
 void DetectTabLanguageFunction::GotLanguage(const std::string& language) {
   result_.reset(Value::CreateStringValue(language.c_str()));
   SendResponse(true);
 
   Release();  // Balanced in Run()
 }