Remove FwlEventMask

The only value being set from the enum was the All Mask. This was always set
through the default value in the methods. This Cl removes the mask code completely
and updates surrounding code as needed.

Review-Url: https://codereview.chromium.org/2515243003
diff --git a/xfa/fwl/core/cfwl_eventtarget.h b/xfa/fwl/core/cfwl_eventtarget.h
index b7e43ce..3ed8e9a 100644
--- a/xfa/fwl/core/cfwl_eventtarget.h
+++ b/xfa/fwl/core/cfwl_eventtarget.h
@@ -7,6 +7,8 @@
 #ifndef XFA_FWL_CORE_CFWL_EVENTTARGET_H_
 #define XFA_FWL_CORE_CFWL_EVENTTARGET_H_
 
+#include <set>
+
 #include "core/fxcrt/fx_basic.h"
 #include "xfa/fwl/core/cfwl_event.h"
 
@@ -18,17 +20,14 @@
   explicit CFWL_EventTarget(IFWL_Widget* pListener);
   ~CFWL_EventTarget();
 
-  int32_t SetEventSource(IFWL_Widget* pSource,
-                         uint32_t dwFilter = FWL_EVENT_ALL_MASK);
+  void SetEventSource(IFWL_Widget* pSource);
   bool ProcessEvent(CFWL_Event* pEvent);
 
   bool IsInvalid() const { return m_bInvalid; }
   void FlagInvalid() { m_bInvalid = true; }
 
  private:
-  bool IsFilterEvent(CFWL_Event* pEvent, uint32_t dwFilter) const;
-
-  CFX_MapPtrTemplate<void*, uint32_t> m_eventSources;
+  std::set<IFWL_Widget*> m_widgets;
   IFWL_Widget* m_pListener;
   bool m_bInvalid;
 };