Bug 838256, part 1 - Initial work on the layout pieces for <input type=range>. DONTBUILD separately from jwatt's changeset (the next one) to finish this work. r=dholbert for the combined diff.
Bug 838256, part 2 - Overhaul and complete the layout pieces for <input type=range>. r=dholbert for the combined diff with the previous changeset.
Bug 838256 - Reftests and crashtests for <input type=range>. r=dholbert.