Revert 154887 "New positioning model: Borders"

This CL caused compile failures on Chrome OS build bots.
http://build.chromium.org/p/chromium.chrome/builders/Google%20Chrome%20ChromeOS/builds/56352/steps/compile/logs/stdio

> 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/20107003

TBR=bjonesbe@adobe.com

Review URL: https://codereview.chromium.org/20145006

git-svn-id: svn://svn.chromium.org/blink/trunk@154909 bbb929c8-8fbe-4397-9dbb-9b2b20218538