Merge to XFA: Use override in more classes in fpdfsdk/

R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1287193005 .

(cherry picked from commit 0f6b51c0fdd14f5762bf3c7412ac59c825443cc3)

Review URL: https://codereview.chromium.org/1288393004 .
diff --git a/fpdfsdk/src/javascript/event.cpp b/fpdfsdk/src/javascript/event.cpp
index 4bcdcce..492f225 100644
--- a/fpdfsdk/src/javascript/event.cpp
+++ b/fpdfsdk/src/javascript/event.cpp
@@ -50,7 +50,8 @@
 
 event::event(CJS_Object* pJsObject) : CJS_EmbedObj(pJsObject) {}
 
-event::~event(void) {}
+event::~event() {
+}
 
 FX_BOOL event::change(IFXJS_Context* cc,
                       CJS_PropValue& vp,