Make the I in IFormFiller explicit

fpdfsdk/formfiller/cffl_checkbox.cpp

Index: fpdfsdk/formfiller/cffl_checkbox.cpp
diff --git a/fpdfsdk/formfiller/cffl_checkbox.cpp b/fpdfsdk/formfiller/cffl_checkbox.cpp
index ef1bf18ea659151456a4ce80587f4cef2790e0f0..01f1a2a08c063b4aedc97f5fd7382962f85aeb5a 100644
--- a/fpdfsdk/formfiller/cffl_checkbox.cpp
+++ b/fpdfsdk/formfiller/cffl_checkbox.cpp
@@ -42,17 +42,13 @@ FX_BOOL CFFL_CheckBox::OnChar(CPDFSDK_Annot* pAnnot,
   switch (nChar) {
     case FWL_VKEY_Return:
     case FWL_VKEY_Space: {
-      CFFL_IFormFiller* pIFormFiller = m_pEnv->GetIFormFiller();
-      ASSERT(pIFormFiller);
-
       CPDFSDK_PageView* pPageView = pAnnot->GetPageView();
       ASSERT(pPageView);
 
       FX_BOOL bReset = FALSE;
       FX_BOOL bExit = FALSE;
-
-      pIFormFiller->OnButtonUp(m_pWidget, pPageView, bReset, bExit, nFlags);
-
+      m_pEnv->GetInteractiveFormFiller()->OnButtonUp(m_pWidget, pPageView,
+                                                     bReset, bExit, nFlags);
       if (bReset)
         return TRUE;
       if (bExit)