Confine CFX_SystemHandler to fpdfsdk/ layer.

All other layers now use one of the interface classes.

Change-Id: Iaf7d510bcb9c363a3772c8e8f66882c3613a3815
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/58952
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/fpdfsdk/cpdfsdk_formfillenvironment.h b/fpdfsdk/cpdfsdk_formfillenvironment.h
index c0b210c..c4afcac 100644
--- a/fpdfsdk/cpdfsdk_formfillenvironment.h
+++ b/fpdfsdk/cpdfsdk_formfillenvironment.h
@@ -15,11 +15,11 @@
 #include "core/fpdfapi/page/cpdf_page.h"
 #include "core/fpdfapi/parser/cpdf_document.h"
 #include "core/fxcrt/observed_ptr.h"
+#include "fpdfsdk/cfx_systemhandler.h"
 #include "fpdfsdk/cpdfsdk_annot.h"
 #include "public/fpdf_formfill.h"
 
 class CFFL_InteractiveFormFiller;
-class CFX_SystemHandler;
 class CPDFSDK_ActionHandler;
 class CPDFSDK_AnnotHandlerMgr;
 class CPDFSDK_InteractiveForm;
@@ -197,7 +197,7 @@
   void JS_docSubmitForm(void* formData, int length, const WideString& URL);
 
   ByteString GetAppName() const { return ByteString(); }
-  CFX_SystemHandler* GetSysHandler() const { return m_pSysHandler.get(); }
+  IPWL_SystemHandler* GetSysHandler() const { return m_pSysHandler.get(); }
   FPDF_FORMFILLINFO* GetFormFillInfo() const { return m_pInfo; }
 
   // Creates if not present.