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: http://src.chromium.org/svn/trunk/src/build@70539 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -323,6 +323,10 @@
     # Use OpenSSL instead of NSS. Under development: see http://crbug.com/62803
     'use_openssl%': 0,
 
+    # Use Harfbuzz-NG instead of Harfbuzz.
+    # Under development: http://crbug.com/68551
+    'use_harfbuzz_ng%': 0,
+
     'conditions': [
       ['OS=="linux" or OS=="freebsd" or OS=="openbsd"', {
         # This will set gcc_version to XY if you are running gcc X.Y.*.