WebView: Cleanup class/struct forward declarations

android_webview/browser/aw_browser_main_parts.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 ANDROID_WEBVIEW_BROWSER_AW_BROWSER_MAIN_PARTS_H_
 #define ANDROID_WEBVIEW_BROWSER_AW_BROWSER_MAIN_PARTS_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "content/public/browser/browser_main_parts.h"
 
 namespace base {
 class MessageLoop;
 }
 
 namespace android_webview {
 
-class AwBrowserContext;
 class AwContentBrowserClient;
 
 class AwBrowserMainParts : public content::BrowserMainParts {
  public:
   explicit AwBrowserMainParts(AwContentBrowserClient* browser_client);
   ~AwBrowserMainParts() override;
 
   // Overriding methods from content::BrowserMainParts.
   void PreEarlyInitialization() override;
   int PreCreateThreads() override;
   void PreMainMessageLoopRun() override;
   bool MainMessageLoopRun(int* result_code) override;
 
  private:
   // Android specific UI MessageLoop.
   std::unique_ptr<base::MessageLoop> main_message_loop_;
 
   AwContentBrowserClient* browser_client_;
 
   DISALLOW_COPY_AND_ASSIGN(AwBrowserMainParts);
 };
 
 }  // namespace android_webview
 
 #endif  // ANDROID_WEBVIEW_BROWSER_AW_BROWSER_MAIN_PARTS_H_