Add support for DOM Level 3 WheelEvent

Add support for DOM Level 3 WheelEvent:
http://www.w3.org/TR/DOM-Level-3-Events/#events-WheelEvent

Full support is implemented except for the DeltaZ property which had
no equivalent in the previous 'mousewheel' event.

Firefox and IE10 already support it so it increases our cross-browser
compatibility.

The non-standard 'mousewheel' event is still supported for backward
compatibility.

BUG=227454

Review URL: https://chromiumcodereview.appspot.com/22859012

git-svn-id: svn://svn.chromium.org/blink/trunk@156404 bbb929c8-8fbe-4397-9dbb-9b2b20218538
More refactoring to get rid of DOMDataStore::getWrapper call sites.

It's unsafe handle access and going away.

BUG=236290

Review URL: https://chromiumcodereview.appspot.com/22964006

git-svn-id: svn://svn.chromium.org/blink/trunk@156405 bbb929c8-8fbe-4397-9dbb-9b2b20218538