Add hb-ot-font.cc and hb-ot-font.h

Add hb-ot-font.cc and hb-ot-font.h

This patch includes hb-ot-font.cc and hb-ot-font.h into our builds.
These files are available since harfbuzz-ng 0.9.28.

This patch also contains a cherry-pick below to fix a build warning.
https://github.com/behdad/harfbuzz/commit/f1b44303df0712b433e35e1e1e75115c353b279e

BUG=383580
Committed: https://crrev.com/0313dc8a6205bf6c7934c7e7927604eac1d9b027
Cr-Commit-Position: refs/heads/master@{#331666}

[kojii, 2015-05-20 17:31:03]

kojii@chromium.org changed reviewers:
+ behdad@chromium.org, dominik.rottsches@intel.com, eae@chromium.org

[kojii, 2015-05-20 17:31:04]

PTAL.

[kojii, 2015-05-26 09:36:32]

Patchset #2 (id:20001) has been deleted

[eae, 2015-05-26 22:39:04]

Do we need those files? Given that no tests needed updating and there are no
corresponding blink-side change I'm curious to learn what they're needed for.

[behdad_google, 2015-05-26 22:44:34]

On 2015/05/26 22:39:04, eae wrote:
> Do we need those files? Given that no tests needed updating and there are no
> corresponding blink-side change I'm curious to learn what they're needed for.

Long-term we want to move to using that instead of Skia HB font callbacks...

[eae, 2015-05-26 22:45:21]

On 2015/05/26 22:44:34, behdad_google wrote:
> On 2015/05/26 22:39:04, eae wrote:
> > Do we need those files? Given that no tests needed updating and there are no
> > corresponding blink-side change I'm curious to learn what they're needed
for.
> 
> Long-term we want to move to using that instead of Skia HB font callbacks...

Ok, I'd rather wait to add these files until we need them though.

[kojii, 2015-05-27 00:09:21]

On 2015/05/26 22:39:04, eae wrote:
> Do we need those files? Given that no tests needed updating and there are no
> corresponding blink-side change I'm curious to learn what they're needed for.

The Unicode variation selector suppprt I'm preparing use code in this file. UVS
will then be the early adapter of the long term plan Behdad mentioned.

[eae, 2015-05-27 19:40:41]

LGTM

[eae, 2015-05-27 19:40:46]

The CQ bit was checked by eae@chromium.org

[commit-bot: I haz the power, 2015-05-27 19:41:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1143213003/40001

[commit-bot: I haz the power, 2015-05-27 21:59:56]

Committed patchset #2 (id:40001)

[commit-bot: I haz the power, 2015-05-27 22:00:42]

Patchset 2 (id:??) landed as
https://crrev.com/0313dc8a6205bf6c7934c7e7927604eac1d9b027
Cr-Commit-Position: refs/heads/master@{#331666}