Remove Password Authentication code that is no longer used.

chrome/browser/android/password_authentication_manager.h

-// Copyright 2014 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_ANDROID_PASSWORD_AUTHENTICATION_MANAGER_H_
-#define CHROME_BROWSER_ANDROID_PASSWORD_AUTHENTICATION_MANAGER_H_
-
-#include "base/android/jni_android.h"
-#include "base/callback.h"
-#include "components/autofill/core/common/password_form_fill_data.h"
-
-namespace content {
-class WebContents;
-}
-
-// Manager for authenticating the use of stored passwords.
-class PasswordAuthenticationManager {
- public:
-  // JNI registration
-  static bool RegisterPasswordAuthenticationManager(JNIEnv* env);
-
-  // Request an authentication challenge for the specified webcontents to allow
-  // password autofill.  If the authentication is successful, run the
-  // |success_callback|.
-  static void AuthenticatePasswordAutofill(
-      content::WebContents* web_contents,
-      const base::Closure& success_callback);
-
- private:
-  PasswordAuthenticationManager();
-  ~PasswordAuthenticationManager();
-
-  DISALLOW_COPY_AND_ASSIGN(PasswordAuthenticationManager);
-};
-
-#endif  // CHROME_BROWSER_ANDROID_PASSWORD_AUTHENTICATION_MANAGER_H_