harfbuzz: check in harfbuzz-ng, add gyp define to use it

      This checks in harbuzz-ng b0d396aa88b3cdf8cea896bfeeba197656e1cdb1.

Setting use_harfbuzz_ng to 1 in gyp will cause us to build
harfbuzz-ng in place of harfbuzz.  So far this currently fails to
compile due to all our other code relying on the old API.

BUG=68551
TEST=./build/gyp_chromium -Duse_harfbuzz_ng=1, verify build breaks

Review URL: http://codereview.chromium.org/6052008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@70539 0039d316-1c4b-4281-b951-d872f2087c98