Revert of Remove WheelEvent.initWebKitWheelEvent() (https://codereview.chromium.org/425633002/)

Reason for revert:
This change broke the following browser_tests:
NetInternalsTest.netInternalsTimelineViewDegenerate
NetInternalsTest.netInternalsTimelineViewNoEvents
NetInternalsTest.netInternalsTimelineViewZoomIn
NetInternalsTest.netInternalsTimelineViewZoomOut

http://build.chromium.org/p/chromium.webkit/builders/Linux%20Tests/builds/38303

Original issue's description:
> Remove WheelEvent.initWebKitWheelEvent()
> 
> Intent to Deprecate and Remove:
> https://groups.google.com/a/chromium.org/d/msg/blink-dev/h_GoezQ4MQ4/Q5abFkhA76sJ
> 
> BUG=398422
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=179183

TBR=tkent@chromium.org,philipj@opera.com
NOTREECHECKS=true
NOTRY=true
BUG=398738

Review URL: https://codereview.chromium.org/429803002

git-svn-id: svn://svn.chromium.org/blink/trunk@179198 bbb929c8-8fbe-4397-9dbb-9b2b20218538