[Prerender] Get the prerender mode from Finch field trial.

chrome/browser/ui/webui/net_internals/net_internals_ui_browsertest.h

 // Copyright (c) 2012 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_NET_INTERNALS_NET_INTERNALS_UI_BROWSERTEST_H_
 #define CHROME_BROWSER_UI_WEBUI_NET_INTERNALS_NET_INTERNALS_UI_BROWSERTEST_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "chrome/test/base/web_ui_browser_test.h"
 
 class GURL;
 
 class NetInternalsTest : public WebUIBrowserTest {
  protected:
   NetInternalsTest();
   ~NetInternalsTest() override;
 
  private:
   class MessageHandler;
 
   // InProcessBrowserTest overrides.
-  void SetUpCommandLine(base::CommandLine* command_line) override;
   void SetUpOnMainThread() override;
 
   // WebUIBrowserTest implementation.
   content::WebUIMessageHandler* GetMockMessageHandler() override;
 
   GURL CreatePrerenderLoaderUrl(const GURL& prerender_url);
 
   // Attempts to start the test server.  Returns true on success or if the
   // TestServer is already started.
   bool StartTestServer();
 
   std::unique_ptr<MessageHandler> message_handler_;
 
   // True if the test server has already been successfully started.
   bool test_server_started_;
 
   DISALLOW_COPY_AND_ASSIGN(NetInternalsTest);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_NET_INTERNALS_NET_INTERNALS_UI_BROWSERTEST_H_