Roll HarfBuzz to 1.8.8

https://chromium.googlesource.com/external/github.com/harfbuzz/harfbuzz/+log/b6fdcf4f8bd09e065c767939125861c9dc8ff18f..7112c6413ca7a1773847fe258145cc5162420953

Bug: 873568
Change-Id: Ia6a7c9baa0bdce0bc3d4dc50c75c70c0dbbb6555
Tbr: behdad@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/1174951
Commit-Queue: Emil A Eklund <eae@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583331}

DEPS

@@ -161,7 +161,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling HarfBuzz
   # and whatever else without interference from each other.
-  'harfbuzz_revision': 'b6fdcf4f8bd09e065c767939125861c9dc8ff18f',
+  'harfbuzz_revision': '22defe0965adddaa09eebc13df7fa6c64e2abba3',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling catapult
   # and whatever else without interference from each other.

third_party/harfbuzz-ng/README.chromium

 Name: harfbuzz-ng
 Short Name: harfbuzz-ng
 URL: http://harfbuzz.org
-Version: 1.8.7
-Date: 20180809
-Revision: b6fdcf4f8bd09e065c767939125861c9dc8ff18f
+Version: 1.8.8
+Date: 20180815
+Revision: 22defe0965adddaa09eebc13df7fa6c64e2abba3
 Security Critical: yes
 License: MIT
 License File: src/COPYING