Random Gamepad cleanup
https://bugs.webkit.org/show_bug.cgi?id=136193

Reviewed by Sam Weinig.

No new tests (Not tested yet, and no change in behavior anyways)

- Use DOMWindow WeakPtrs when iterating
- More references instead of pointers

* Modules/gamepad/GamepadEvent.cpp:
(WebCore::GamepadEvent::GamepadEvent):
* Modules/gamepad/GamepadEvent.h:
(WebCore::GamepadEvent::create):

* Modules/gamepad/GamepadManager.cpp:
(WebCore::GamepadManager::platformGamepadDisconnected):
(WebCore::GamepadManager::makeGamepadVisible):
* Modules/gamepad/NavigatorGamepad.cpp:
(WebCore::NavigatorGamepad::gamepadFromPlatformGamepad):
(WebCore::NavigatorGamepad::gamepadAtIndex): Deleted.
* Modules/gamepad/NavigatorGamepad.h:

* page/DOMWindow.cpp:
(WebCore::DOMWindow::DOMWindow):
* page/DOMWindow.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@172890 268f45cc-cd09-0410-ab3c-d52691b4dbfc