Get rid of NULLs in fpdfsdk/

Review-Url: https://codereview.chromium.org/2031653003
diff --git a/fpdfsdk/formfiller/cffl_formfiller.cpp b/fpdfsdk/formfiller/cffl_formfiller.cpp
index 8ee6da3..d7bc958 100644
--- a/fpdfsdk/formfiller/cffl_formfiller.cpp
+++ b/fpdfsdk/formfiller/cffl_formfiller.cpp
@@ -88,7 +88,8 @@
   } else {
     CPDFSDK_Widget* pWidget = (CPDFSDK_Widget*)pAnnot;
     if (CFFL_IFormFiller::IsVisible(pWidget))
-      pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Normal, NULL);
+      pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Normal,
+                              nullptr);
   }
 }
 
@@ -98,7 +99,7 @@
                                      CFX_Matrix* pUser2Device,
                                      uint32_t dwFlags) {
   CPDFSDK_Widget* pWidget = (CPDFSDK_Widget*)pAnnot;
-  pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Normal, NULL);
+  pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Normal, nullptr);
 }
 
 void CFFL_FormFiller::OnCreate(CPDFSDK_Annot* pAnnot) {}
@@ -293,7 +294,7 @@
   ASSERT(m_pApp);
 
   PWL_CREATEPARAM cp;
-  cp.pParentWnd = NULL;
+  cp.pParentWnd = nullptr;
   cp.pProvider = this;
   cp.rcRectWnd = GetPDFWindowRect();
 
@@ -690,23 +691,25 @@
   CPDF_FormControl::HighlightingMode eHM = pCtrl->GetHighlightingMode();
 
   if (eHM != CPDF_FormControl::Push) {
-    pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Normal, NULL);
+    pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Normal, nullptr);
     return;
   }
 
   if (m_bMouseDown) {
     if (pWidget->IsWidgetAppearanceValid(CPDF_Annot::Down))
-      pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Down, NULL);
+      pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Down, nullptr);
     else
-      pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Normal, NULL);
+      pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Normal,
+                              nullptr);
   } else if (m_bMouseIn) {
     if (pWidget->IsWidgetAppearanceValid(CPDF_Annot::Rollover))
       pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Rollover,
-                              NULL);
+                              nullptr);
     else
-      pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Normal, NULL);
+      pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Normal,
+                              nullptr);
   } else {
-    pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Normal, NULL);
+    pWidget->DrawAppearance(pDevice, pUser2Device, CPDF_Annot::Normal, nullptr);
   }
 }