Cleanup remaining class/struct fwd declarations

headless/lib/browser/headless_browser_main_parts.h

 // Copyright 2015 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 HEADLESS_LIB_BROWSER_HEADLESS_BROWSER_MAIN_PARTS_H_
 #define HEADLESS_LIB_BROWSER_HEADLESS_BROWSER_MAIN_PARTS_H_
 
 #include <memory>
 
 #include "content/public/browser/browser_main_parts.h"
 #include "headless/public/headless_browser.h"
 
 namespace headless {
 
-class HeadlessBrowserContextImpl;
 class HeadlessBrowserImpl;
 
 class HeadlessBrowserMainParts : public content::BrowserMainParts {
  public:
   explicit HeadlessBrowserMainParts(HeadlessBrowserImpl* browser);
   ~HeadlessBrowserMainParts() override;
 
   // content::BrowserMainParts implementation:
   void PreMainMessageLoopRun() override;
   void PostMainMessageLoopRun() override;
 
  private:
   HeadlessBrowserImpl* browser_;  // Not owned.
 
   bool devtools_http_handler_started_;
 
   DISALLOW_COPY_AND_ASSIGN(HeadlessBrowserMainParts);
 };
 
 }  // namespace headless
 
 #endif  // HEADLESS_LIB_BROWSER_HEADLESS_BROWSER_MAIN_PARTS_H_