Consolidate javascript_dialog_manager.h and javascript_dialog_manager_impl.h

components/app_modal_dialogs/BUILD.gn

 # 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.
 
 import("//build/config/ui.gni")
 
 static_library("app_modal_dialogs") {
   sources = [
     "app_modal_dialog.cc",
     "app_modal_dialog.h",
     "app_modal_dialog_queue.cc",
     "app_modal_dialog_queue.h",
     "app_modal_dialog_test_util.h",
     "javascript_app_modal_dialog.cc",
     "javascript_app_modal_dialog.h",
     "javascript_dialog_extension_client.h",
     "javascript_dialog_manager.cc",
     "javascript_dialog_manager.h",
-    "javascript_dialog_manager_impl.cc",
-    "javascript_dialog_manager_impl.h",
     "javascript_native_dialog_factory.h",
     "native_app_modal_dialog.h"
   ]
 
   deps = [
     "//components/strings",
     "//content/public/browser",
     "//content/public/common",
     "//skia",
   ]
 
   if (use_aura) {
     deps += [ "//ui/aura" ]
   }
 
   if (toolkit_views && !is_mac) {
     sources += [
       "views/javascript_app_modal_dialog_views.h",
       "views/javascript_app_modal_dialog_views.cc",
     ]
   }
 }