Make the I in IFormFiller explicit

Typically the I prefix means Interface, except for CFFL_IFormFiller where it
means Interactive. Rename CFFL_IFormFiller to CFFL_InteractiveFormFiller to
make the meaning explicit.

Review-Url: https://codereview.chromium.org/2357203003
diff --git a/fpdfsdk/cpdfsdk_interform.cpp b/fpdfsdk/cpdfsdk_interform.cpp
index e9fb5b4..ce6206a 100644
--- a/fpdfsdk/cpdfsdk_interform.cpp
+++ b/fpdfsdk/cpdfsdk_interform.cpp
@@ -342,10 +342,10 @@
 
     if (CPDFSDK_Widget* pWidget = GetWidget(pFormCtrl, false)) {
       CPDFSDK_Environment* pEnv = m_pDocument->GetEnv();
-      CFFL_IFormFiller* pIFormFiller = pEnv->GetIFormFiller();
       UnderlyingPageType* pPage = pWidget->GetUnderlyingPage();
       CPDFSDK_PageView* pPageView = m_pDocument->GetPageView(pPage, false);
-      FX_RECT rcBBox = pIFormFiller->GetViewBBox(pPageView, pWidget);
+      FX_RECT rcBBox =
+          pEnv->GetInteractiveFormFiller()->GetViewBBox(pPageView, pWidget);
 
       pEnv->Invalidate(pPage, rcBBox.left, rcBBox.top, rcBBox.right,
                        rcBBox.bottom);