Dispatch change event for input type=checkbox when checked but value is null

Source/core/html/forms/InputType.h

Index: Source/core/html/forms/InputType.h
diff --git a/Source/core/html/forms/InputType.h b/Source/core/html/forms/InputType.h
index 20f415a8329aebd92d56ee858e402ad4c3361353..c5fa3aebd8e87f361c5fa3de259a721116e5b755 100644
--- a/Source/core/html/forms/InputType.h
+++ b/Source/core/html/forms/InputType.h
@@ -220,6 +220,8 @@ public:
     virtual bool shouldSubmitImplicitly(Event*) OVERRIDE;
     virtual bool hasCustomFocusLogic() const OVERRIDE;
 
+    virtual bool shouldDispatchFormControlChangeEvent(String&, String&);
+
 protected:
     InputType(HTMLInputElement& element) : InputTypeView(element) { }
     Chrome* chrome() const;