Revert of [headless] Use individual aura::WindowTreeHosts per WebContents.

headless/lib/browser/headless_web_contents_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_WEB_CONTENTS_IMPL_H_
 #define HEADLESS_LIB_BROWSER_HEADLESS_WEB_CONTENTS_IMPL_H_
 
 #include <list>
 #include <memory>
 #include <string>
 #include <unordered_map>
 
 #include "content/public/browser/render_process_host_observer.h"
 #include "content/public/browser/web_contents_observer.h"
-#include "headless/lib/browser/headless_window_tree_host.h"
 #include "headless/public/headless_devtools_target.h"
 #include "headless/public/headless_export.h"
 #include "headless/public/headless_web_contents.h"
 
 namespace content {
 class DevToolsAgentHost;
 class WebContents;
 }
 
 namespace gfx {
@@ skipping 46 matching lines @@
   content::WebContents* web_contents() const;
   bool OpenURL(const GURL& url);
 
   void Close() override;
 
   std::string GetDevToolsAgentHostId();
 
   HeadlessBrowserImpl* browser() const;
   HeadlessBrowserContextImpl* browser_context() const;
 
-  void set_window_tree_host(std::unique_ptr<HeadlessWindowTreeHost> host) {
-    window_tree_host_ = std::move(host);
-  }
-  HeadlessWindowTreeHost* window_tree_host() const {
-    return window_tree_host_.get();
-  }
-
  private:
   // Takes ownership of |web_contents|.
   HeadlessWebContentsImpl(content::WebContents* web_contents,
                           HeadlessBrowserContextImpl* browser_context);
 
   void InitializeScreen(const gfx::Size& initial_size);
 
   using MojoService = HeadlessWebContents::Builder::MojoService;
 
   class Delegate;
   std::unique_ptr<Delegate> web_contents_delegate_;
-  std::unique_ptr<HeadlessWindowTreeHost> window_tree_host_;
   std::unique_ptr<content::WebContents> web_contents_;
   scoped_refptr<content::DevToolsAgentHost> agent_host_;
   std::list<MojoService> mojo_services_;
 
   HeadlessBrowserContextImpl* browser_context_;      // Not owned.
   content::RenderProcessHost* render_process_host_;  // Not owned.
 
   using ObserverMap =
       std::unordered_map<HeadlessWebContents::Observer*,
                          std::unique_ptr<WebContentsObserverAdapter>>;
   ObserverMap observer_map_;
 
   DISALLOW_COPY_AND_ASSIGN(HeadlessWebContentsImpl);
 };
 
 }  // namespace headless
 
 #endif  // HEADLESS_LIB_BROWSER_HEADLESS_WEB_CONTENTS_IMPL_H_