Cherry pick HarfBuzz white-space fix

Cherry pick HarfBuzz white-space fix

Cherry pick HarfBuzz change 24f17afeafd40ff77177ed42c9007a0f34fcbb78 for
a right-to-left trailing whitespace issue that is rather serious and can
cause asserts and incorrect behavior on Mac OS. Safe to merge to branch.

R=jchaffraix@chromium.org, behdad@chromium.org
BUG=476913
TEST=fast/text/unicode-fallback-font.html

Committed: https://crrev.com/606c77e1b6c10624bffa4f1cdef74f1e055cd93d
Cr-Commit-Position: refs/heads/master@{#331445}

[behdad_google, 2015-05-26 21:03:38]

behdad@google.com changed reviewers:
+ behdad@google.com

[behdad_google, 2015-05-26 21:03:38]

lgtm

[Julien - ping for review, 2015-05-26 21:45:40]

rubber-stamp lgtm.

[Julien - ping for review, 2015-05-26 21:45:45]

The CQ bit was checked by jchaffraix@chromium.org

[commit-bot: I haz the power, 2015-05-26 21:46:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1158783002/1

[commit-bot: I haz the power, 2015-05-26 21:56:16]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-26 21:57:13]

Patchset 1 (id:??) landed as
https://crrev.com/606c77e1b6c10624bffa4f1cdef74f1e055cd93d
Cr-Commit-Position: refs/heads/master@{#331445}