Handle potential overflow of gamepadEventListenerCount.

https://bugs.webkit.org/show_bug.cgi?id=256205.
rdar://80838189.

Reviewed by Ryosuke Niwa.

m_gamepadEventListenerCount can overflow if addEventListener() is called UINT_MAX+1 times.
Once the window is freed, we will be left with a dangling pointer in the GamepadManager.
This change adds a flag to check for overflow and keep the behavior same in the event of overflow..

* Source/WebCore/page/DOMWindow.cpp:
(WebCore::DOMWindow::~DOMWindow):
(WebCore::DOMWindow::incrementGamepadEventListenerCount):
(WebCore::DOMWindow::decrementGamepadEventListenerCount):
* Source/WebCore/page/DOMWindow.h:

Canonical link: https://commits.webkit.org/259548.729@safari-7615-branch

Source/WebCore/page/DOMWindow.h

@@ -479,7 +479,7 @@ class DOMWindow final
 #endif
 
 #if ENABLE(GAMEPAD)
-    unsigned m_gamepadEventListenerCount { 0 };
+    uint64_t m_gamepadEventListenerCount { 0 };
 #endif
 
     mutable RefPtr<Storage> m_sessionStorage;