Add Harfbuzz to third_party and Skia support for such.

      Harfbuzz is an open source library which is a unification of the Qt
and Pango shaping engines. We'll be using it on Chromium Linux to
perform complex text shaping.

Additionally, we add support for Harfbuzz into Skia, guarded by
SKIA_HARFBUZZ.

http://codereview.chromium.org/63035/show


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@13214 0039d316-1c4b-4281-b951-d872f2087c98