headless: Implement screenshot capturing

headless/lib/browser/headless_browser_impl.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_IMPL_H_
 #define HEADLESS_LIB_BROWSER_HEADLESS_BROWSER_IMPL_H_
 
 #include "headless/public/headless_browser.h"
 
 #include <memory>
 #include <unordered_map>
+#include <vector>
 
 #include "base/synchronization/lock.h"
 #include "headless/lib/browser/headless_web_contents_impl.h"
 
 namespace aura {
 class WindowTreeHost;
 
 namespace client {
 class WindowTreeClient;
 }
 }
 
 namespace headless {
 
 class HeadlessBrowserContext;
 class HeadlessBrowserMainParts;
 
 class HeadlessBrowserImpl : public HeadlessBrowser {
  public:
   HeadlessBrowserImpl(
       const base::Callback<void(HeadlessBrowser*)>& on_start_callback,
       HeadlessBrowser::Options options);
   ~HeadlessBrowserImpl() override;
 
   // HeadlessBrowser implementation:
   HeadlessWebContents* CreateWebContents(const GURL& initial_url,
                                          const gfx::Size& size) override;
   scoped_refptr<base::SingleThreadTaskRunner> BrowserMainThread()
       const override;
+  scoped_refptr<base::SingleThreadTaskRunner> BrowserFileThread()
+      const override;
 
   void Shutdown() override;
 
   std::vector<HeadlessWebContents*> GetAllWebContents() override;
 
   void set_browser_main_parts(HeadlessBrowserMainParts* browser_main_parts);
   HeadlessBrowserMainParts* browser_main_parts() const;
 
   HeadlessBrowserContext* browser_context() const;
 
@@ skipping 15 matching lines @@
  protected:
   base::Callback<void(HeadlessBrowser*)> on_start_callback_;
   HeadlessBrowser::Options options_;
   HeadlessBrowserMainParts* browser_main_parts_;  // Not owned.
   std::unique_ptr<aura::WindowTreeHost> window_tree_host_;
   std::unique_ptr<aura::client::WindowTreeClient> window_tree_client_;
 
   std::unordered_map<HeadlessWebContents*, std::unique_ptr<HeadlessWebContents>>
       web_contents_;
 
+ private:
   DISALLOW_COPY_AND_ASSIGN(HeadlessBrowserImpl);
 };
 
 }  // namespace headless
 
 #endif  // HEADLESS_LIB_BROWSER_HEADLESS_BROWSER_IMPL_H_