Remove -webkit-line-grid, -webkit-line-snap and -webkit-line-align

Features we inherited from Apple's WebKit, but do not comply with
in-progress standards work:
http://dev.w3.org/csswg/css-line-grid/
and currently are not under active development in Blink. We can remove
these now and add back standards-compliant versions at a later date.

Usage:
webkit-line-grid: 0.00734% 
webkit-line-snap: 0.00726%
webkit-line-align: 0.00720%

Intent To Remove:
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/nGFTVcfk8dY

BUG=343808

Review URL: https://codereview.chromium.org/146093005

git-svn-id: svn://svn.chromium.org/blink/trunk@167181 bbb929c8-8fbe-4397-9dbb-9b2b20218538