Remove include only fwl.h and IWYU.

xfa/include/fwl/core/fwl_app.h

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef XFA_INCLUDE_FWL_CORE_FWL_APP_H_
 #define XFA_INCLUDE_FWL_CORE_FWL_APP_H_
 
-class IFWL_NoteThread;
+#include "core/include/fxcrt/fx_string.h"
+#include "xfa/include/fwl/core/fwl_thread.h"
+
 class IFWL_AdapterNative;
 class IFWL_Widget;
 class IFWL_WidgetMgr;
 class IFWL_ThemeProvider;
 class IFWL_AdapterWidgetMgr;
 
 class IFWL_App : public IFWL_NoteThread {
  public:
   static IFWL_App* Create(IFWL_AdapterNative* pAdapter);
 
@@ skipping 12 matching lines @@
 void FWL_SetApp(IFWL_App* pApp);
 IFWL_AdapterNative* FWL_GetAdapterNative();
 IFWL_AdapterWidgetMgr* FWL_GetAdapterWidgetMgr();
 IFWL_ThemeProvider* FWL_GetThemeProvider();
 extern FWL_ERR FWL_Execute(const CFX_WideStringC& wsExecutable,
                            const CFX_WideStringC& wsParameters);
 FWL_ERR FWL_SetFullScreen(IFWL_Widget* pWidget, FX_BOOL bFullScreen);
 FX_BOOL FWL_AppIsActived();
 
 #endif  // XFA_INCLUDE_FWL_CORE_FWL_APP_H_