Replace WebUI::tab_contents() with web_contents() and switch all users to use web_contents.h inst...

chrome/browser/ui/webui/tracing_ui.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_TRACING_UI_H_
 #define CHROME_BROWSER_UI_WEBUI_TRACING_UI_H_
 #pragma once
 
 #include "chrome/browser/ui/webui/chrome_web_ui.h"
 
 // The C++ back-end for the chrome://tracing webui page.
 class TracingUI : public ChromeWebUI {
  public:
-  explicit TracingUI(TabContents* contents);
+  explicit TracingUI(content::WebContents* contents);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TracingUI);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_TRACING_UI_H_