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

Source/core/html/HTMLTextFormControlElement.cpp

Index: Source/core/html/HTMLTextFormControlElement.cpp
diff --git a/Source/core/html/HTMLTextFormControlElement.cpp b/Source/core/html/HTMLTextFormControlElement.cpp
index c3f751a63f54d4eb643bdb97275b0ecbe1ae555c..bf3597a17159f2e0cad756e6e8be0ffc25b2bc4c 100644
--- a/Source/core/html/HTMLTextFormControlElement.cpp
+++ b/Source/core/html/HTMLTextFormControlElement.cpp
@@ -182,11 +182,17 @@ void HTMLTextFormControlElement::select()
     setSelectionRange(0, numeric_limits<int>::max(), SelectionHasNoDirection);
 }
 
+bool HTMLTextFormControlElement::shouldDispatchFormControlChangeEvent(String& oldValue, String& newValue)
+{
+    return !equalIgnoringNullity(oldValue, newValue);
+}
+
 void HTMLTextFormControlElement::dispatchFormControlChangeEvent()
 {
-    if (!equalIgnoringNullity(m_textAsOfLastFormControlChangeEvent, value())) {
+    String newValue = value();
+    if (shouldDispatchFormControlChangeEvent(m_textAsOfLastFormControlChangeEvent, newValue)) {
         dispatchChangeEvent();
-        setTextAsOfLastFormControlChangeEvent(value());
+        setTextAsOfLastFormControlChangeEvent(newValue);
     }
     setChangedSinceLastFormControlChangeEvent(false);
 }