Remove test fast/multicol/newmulticol/columns-shorthand-parsing.html

This test isn't very valuable, since there are plenty of balancing tests
already. This test attempted to compare rendering between the old and the
new multicol implementations, and for some reason it fails on Mac, albeit
not visibly to the naked eye.

BUG=254219

Review URL: https://chromiumcodereview.appspot.com/20228003

git-svn-id: svn://svn.chromium.org/blink/trunk@154961 bbb929c8-8fbe-4397-9dbb-9b2b20218538
New positioning model: Borders

Converting to the shape coordinate system was not properly accounting
for borders and padding. This has been fixed and a new convienence
method added because of the added complexity of the conversion.

This is a port from WebKit: http://trac.webkit.org/changeset/153058

BUG=260357

Review URL: https://chromiumcodereview.appspot.com/20368002

git-svn-id: svn://svn.chromium.org/blink/trunk@154962 bbb929c8-8fbe-4397-9dbb-9b2b20218538