Count usage of reading HTMLInputElement::checked during click event handler.

Source/core/html/HTMLInputElement.cpp

Index: Source/core/html/HTMLInputElement.cpp
diff --git a/Source/core/html/HTMLInputElement.cpp b/Source/core/html/HTMLInputElement.cpp
index 9ba9afb5bea38fe6ad64b07efa9ce39824ce6faa..f14561f81f06a0416f789f4e2a8c18d358011798 100644
--- a/Source/core/html/HTMLInputElement.cpp
+++ b/Source/core/html/HTMLInputElement.cpp
@@ -903,6 +903,12 @@ void HTMLInputElement::dispatchChangeEventIfNeeded()
         dispatchFormControlChangeEvent();
 }
 
+bool HTMLInputElement::checked() const
+{
+    m_inputType->readingChecked();
+    return m_isChecked;
+}
+
 void HTMLInputElement::setChecked(bool nowChecked, TextFieldEventBehavior eventBehavior)
 {
     if (checked() == nowChecked)