Remove dependency from SignInBrowsertest on tracing events watching

chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h

 // Copyright (c) 2013 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_CHROMEOS_LOGIN_SIGNIN_SCREEN_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_SIGNIN_SCREEN_HANDLER_H_
 
 #include <map>
 #include <memory>
 #include <set>
@@ skipping 216 matching lines @@
   ~SigninScreenHandler() override;
 
   static std::string GetUserLRUInputMethod(const std::string& username);
 
   // Update current input method (namely keyboard layout) in the given IME state
   // to LRU by this user.
   static void SetUserInputMethod(
       const std::string& username,
       input_method::InputMethodManager::State* ime_state);
 
+  // Sets a callback which will be run when the signin UI is shown.
+  static void SetCallbackOnUiShownForTesting(base::Closure callback);
+
   // Shows the sign in screen.
   void Show(const LoginScreenContext& context);
 
   // Sets delegate to be used by the handler. It is guaranteed that valid
   // delegate is set before Show() method will be called.
   void SetDelegate(SigninScreenHandlerDelegate* delegate);
 
   void SetNativeWindowDelegate(NativeWindowDelegate* native_window_delegate);
 
   // NetworkStateInformer::NetworkStateInformerObserver implementation:
@@ skipping 264 matching lines @@
   std::unique_ptr<LoginFeedback> login_feedback_;
 
   base::WeakPtrFactory<SigninScreenHandler> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SigninScreenHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_SIGNIN_SCREEN_HANDLER_H_