Cleanup FWL Event and Message code.

xfa/fxfa/app/xfa_ffcheckbutton.cpp

Index: xfa/fxfa/app/xfa_ffcheckbutton.cpp
diff --git a/xfa/fxfa/app/xfa_ffcheckbutton.cpp b/xfa/fxfa/app/xfa_ffcheckbutton.cpp
index 06e3b2c8b8dbd54c55782d5c1e411bf5281482c9..dab6b2cde0555fe412e8e4dec3389c964877c658 100644
--- a/xfa/fxfa/app/xfa_ffcheckbutton.cpp
+++ b/xfa/fxfa/app/xfa_ffcheckbutton.cpp
@@ -246,13 +246,12 @@ bool CXFA_FFCheckButton::OnLButtonUp(uint32_t dwFlags,
     return false;
 
   SetButtonDown(false);
-  CFWL_MsgMouse ms;
+  CFWL_MsgMouse ms(nullptr, m_pNormalWidget);
   ms.m_dwCmd = FWL_MouseCommand::LeftButtonUp;
   ms.m_dwFlags = dwFlags;
   ms.m_fx = fx;
   ms.m_fy = fy;
   FWLToClient(ms.m_fx, ms.m_fy);
-  ms.m_pDstTarget = m_pNormalWidget;
   TranslateFWLMessage(&ms);
   return true;
 }
@@ -300,8 +299,8 @@ void CXFA_FFCheckButton::OnProcessMessage(CFWL_Message* pMessage) {
 
 void CXFA_FFCheckButton::OnProcessEvent(CFWL_Event* pEvent) {
   CXFA_FFField::OnProcessEvent(pEvent);
-  switch (pEvent->GetClassID()) {
-    case CFWL_EventType::CheckStateChanged: {
+  switch (pEvent->GetType()) {
+    case CFWL_Event::Type::CheckStateChanged: {
       CXFA_EventParam eParam;
       eParam.m_eType = XFA_EVENT_Change;
       m_pDataAcc->GetValue(eParam.m_wsNewText, XFA_VALUEPICTURE_Raw);