https://bugs.webkit.org/show_bug.cgi?id=78457

Reviewed by Hajime Morita.

This patch moves GAMEPAD-specific logic out of Navigator by introducing
the concept of a NavigatorSupplement, analogous to the recently
introduced PageSupplement.

* Modules/gamepad/NavigatorGamepad.cpp:
(WebCore::NavigatorGamepad::from):
(WebCore):
(WebCore::NavigatorGamepad::webkitGamepads):
(WebCore::NavigatorGamepad::gamepads):
* Modules/gamepad/NavigatorGamepad.h:
(NavigatorGamepad):
* WebCore.gypi:
* dom/DeviceMotionController.cpp:
(WebCore::DeviceMotionController::supplementName):
* page/Navigator.cpp:
(WebCore::Navigator::provideSupplement):
(WebCore):
(WebCore::Navigator::requireSupplement):
* page/Navigator.h:
(Navigator):
* page/Page.h:
(Page):
* page/PageSupplement.h:
    - This patch cleans up some nits in PageSupplement.
(WebCore):
(PageSupplement):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@107536 268f45cc-cd09-0410-ab3c-d52691b4dbfc