For a method defined as below: MouseEvent::MouseEvent(const AtomicString& eventType, bool canBubble, bool cancelable, AbstractView* view, int detail, int screenX, int screenY, int clientX, int clientY, bool ctrlKey, bool altKey, bool shiftKey, bool metaKey, unsigned short button, PassRefPtr<EventTarget> relatedTarget) : MouseRelatedEvent(eventType, canBubble, cancelable, WTF::currentTime(), view, detail, IntPoint(screenX, screenY), IntPoint(0, 0), //L135 #if ENABLE(POINTER_LOCK) IntPoint(0, 0), //L137 #endif ctrlKey, altKey, shiftKey, metaKey, false) , m_button(button == (unsigned short)-1 ? 0 : button) , m_buttonDown(button != (unsigned short)-1) , m_relatedTarget(relatedTarget) { initCoordinates(IntPoint(clientX, clientY)); } check-webkit-style will complains: ERROR: Source/WebCore/dom/MouseEvent.cpp:135: Comma should be at the beginning of the line in a member initialization list. [whitespace/init] [4] ERROR: Source/WebCore/dom/MouseEvent.cpp:137: Comma should be at the beginning of the line in a member initialization list. [whitespace/init] [4] Refer to Bug 153903.