Remove WheelEvent.initWebKitWheelEvent()

Intent to Deprecate and Remove:
https://groups.google.com/a/chromium.org/d/msg/blink-dev/h_GoezQ4MQ4/Q5abFkhA76sJ

BUG=398422

Review URL: https://codereview.chromium.org/425633002

git-svn-id: svn://svn.chromium.org/blink/trunk@179183 bbb929c8-8fbe-4397-9dbb-9b2b20218538