Adding option to SkTileGrid for specifying border pixels.

The purpose of this patch is to make it possible for the chromium compositor to
generate a TileGrid structure that is better suited for scaled playback.
Review URL: https://codereview.appspot.com/7300072

git-svn-id: http://skia.googlecode.com/svn/trunk@7680 2bbb7eff-a529-9590-31e7-b0007b416f81
5 files changed