Start proxying CPDFSDK_Document methods through CPDFSDK_FormFillEnvironment

fpdfsdk/cpdfsdk_formfillenvironment.cpp

Index: fpdfsdk/cpdfsdk_formfillenvironment.cpp
diff --git a/fpdfsdk/cpdfsdk_formfillenvironment.cpp b/fpdfsdk/cpdfsdk_formfillenvironment.cpp
index 5b05d0812867168ed3b9eed089c64adec1431696..586a4df583b6888adb6e57e92019a4c49a0b99e6 100644
--- a/fpdfsdk/cpdfsdk_formfillenvironment.cpp
+++ b/fpdfsdk/cpdfsdk_formfillenvironment.cpp
@@ -10,6 +10,7 @@
 
 #include "fpdfsdk/cpdfsdk_annothandlermgr.h"
 #include "fpdfsdk/cpdfsdk_document.h"
+#include "fpdfsdk/cpdfsdk_interform.h"
 #include "fpdfsdk/formfiller/cffl_interactiveformfiller.h"
 #include "fpdfsdk/fsdk_actionhandler.h"
 #include "fpdfsdk/javascript/ijs_runtime.h"
@@ -552,3 +553,7 @@ void CPDFSDK_FormFillEnvironment::PageEvent(int iPageCount,
     m_pInfo->FFI_PageEvent(m_pInfo, iPageCount, dwEventType);
 }
 #endif  // PDF_ENABLE_XFA
+
+CPDFSDK_InterForm* CPDFSDK_FormFillEnvironment::GetInterForm() const {
+  return m_pSDKDoc->GetInterForm();
+}