[WebView] Remove more redundant classes

android_webview/browser/aw_web_preferences_populater.h

-// Copyright 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 ANDROID_WEBVIEW_BROWSER_AW_WEB_PREFERENCES_POPULATER_H_
-#define ANDROID_WEBVIEW_BROWSER_AW_WEB_PREFERENCES_POPULATER_H_
-
-namespace content {
-class WebContents;
-struct WebPreferences;
-}
-
-namespace android_webview {
-
-// Empty base class so this can be destroyed by AwContentBrowserClient.
-class AwWebPreferencesPopulater {
- public:
-  virtual ~AwWebPreferencesPopulater();
-
-  virtual void PopulateFor(content::WebContents* web_contents,
-                           content::WebPreferences* web_prefs) = 0;
-};
-
-}  // namespace android_webview
-
-#endif  // ANDROID_WEBVIEW_BROWSER_AW_WEB_PREFERENCES_POPULATER_H_