Cleanup FWL Event and Message code.

xfa/fwl/core/cfwl_evtmouse.cpp

Index: xfa/fwl/core/cfwl_evtmouse.cpp
diff --git a/xfa/fwl/core/cfwl_evtmouse.cpp b/xfa/fwl/core/cfwl_evtmouse.cpp
index c85172b738d98b2e3dca8cc0671b80717c2c1a87..8bfce8a9c5baffb461c5928d5e8ccbaf2405d866 100644
--- a/xfa/fwl/core/cfwl_evtmouse.cpp
+++ b/xfa/fwl/core/cfwl_evtmouse.cpp
@@ -6,10 +6,10 @@
 
 #include "xfa/fwl/core/cfwl_evtmouse.h"
 
-CFWL_EvtMouse::CFWL_EvtMouse() {}
+CFWL_EvtMouse::CFWL_EvtMouse(CFWL_Widget* pSrcTarget)
+    : CFWL_EvtMouse(pSrcTarget, nullptr) {}
 
-CFWL_EvtMouse::~CFWL_EvtMouse() {}
+CFWL_EvtMouse::CFWL_EvtMouse(CFWL_Widget* pSrcTarget, CFWL_Widget* pDstTarget)
+    : CFWL_Event(CFWL_Event::Type::Mouse, pSrcTarget, pDstTarget) {}
 
-CFWL_EventType CFWL_EvtMouse::GetClassID() const {
-  return CFWL_EventType::Mouse;
-}
+CFWL_EvtMouse::~CFWL_EvtMouse() {}