Remove mojo/apps/js, it is unused

mojo/apps/js/content_handler_impl.h

-// Copyright 2014 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 MOJO_APPS_JS_CONTENT_HANDLER_IMPL_H_
-#define MOJO_APPS_JS_CONTENT_HANDLER_IMPL_H_
-
-#include "mojo/services/public/interfaces/content_handler/content_handler.mojom.h"
-
-namespace mojo {
-namespace apps {
-
-class ApplicationDelegateImpl;
-
-// Starts a new JSApp for each OnConnect call().
-class ContentHandlerImpl : public InterfaceImpl<ContentHandler> {
- public:
-  ContentHandlerImpl(ApplicationDelegateImpl* app_delegate_impl);
-
- private:
-  ~ContentHandlerImpl() override;
-  void OnConnect(const mojo::String& url,
-                 URLResponsePtr content,
-                 InterfaceRequest<ServiceProvider> service_provider) override;
-
-  ApplicationDelegateImpl* app_delegate_impl_;
-};
-
-}  // namespace apps
-}  // namespace mojo
-
-#endif  // MOJO_APPS_JS_CONTENT_HANDLER_IMPL_H_