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

Source/core/html/forms/BaseCheckableInputType.cpp

Index: Source/core/html/forms/BaseCheckableInputType.cpp
diff --git a/Source/core/html/forms/BaseCheckableInputType.cpp b/Source/core/html/forms/BaseCheckableInputType.cpp
index 30156400440150b0968098c8325796af8f4453df..a5785efe91414a6f0ea57eedbf9408bb135b8731 100644
--- a/Source/core/html/forms/BaseCheckableInputType.cpp
+++ b/Source/core/html/forms/BaseCheckableInputType.cpp
@@ -106,6 +106,12 @@ void BaseCheckableInputType::setValue(const String& sanitizedValue, bool, TextFi
     element().setAttribute(valueAttr, AtomicString(sanitizedValue));
 }
 
+void BaseCheckableInputType::readingChecked() const
+{
+    if (m_isInClickHandler)
+        UseCounter::count(element().document(), UseCounter::ReadingCheckedInClickHandler);
+}
+
 bool BaseCheckableInputType::isCheckable()
 {
     return true;