Make -webkit-font-variant-ligatures actually work.

Make -webkit-font-variant-ligatures actually work.

Right now, the complex text path always ligates, even with
-webkit-font-variant-ligatures:no-common-ligatures. Also, discretionary
and historical ligatures don't work.

This is technically tested by fast/text/font-variant-ligatures.html, but
the default font often doesn't have the GSUB ligature features.
I've changed the test to prefer some fonts that are widely available and
actually have GSUB liga for "fi".

BUG=22240, 114235
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166751

[eseidel, 2013-11-21 18:21:39]

Looks like a logical extension of https://codereview.chromium.org/74413002/. 
Behdad is our Harfbuzz expert.  This looks fine to me, but eae is probably your
best blink-side reviewer.

[eae, 2013-11-21 18:28:22]

This is one of those cases where we probably want a pixel test as well given
that the ref test won't catch if ligatures  stop working entirely.

[efidler1, 2013-11-21 18:32:05]

I think the right answer is to add a new font deployed on every platform that
supports lots of features, and change the layout test driver to use that font by
default. I prototyped a modified Liberation Serif that supports kerning,
ligatures, IPA tone letters, etc. It's metric compatible with Times New Roman so
rebaselining might not touch everything. The font is SIL OFL-licensed. I'm not
sure if that'll work for us.

I asked at https://code.google.com/p/chromium/issues/detail?id=313806 whether
doing such a thing is feasible, with no response.

[behdad_google, 2013-11-21 21:16:02]

lgtm

[efidler1, 2013-11-22 19:54:08]

On 2013/11/21 18:28:22, eae wrote:
> This is one of those cases where we probably want a pixel test as well given
> that the ref test won't catch if ligatures  stop working entirely.

I've got another idea.. we can explicitly test against U+FB01 in the expected
file. I think the default fonts on each platform should have a ligated glyph
there.

[efidler1, 2014-02-06 13:55:15]

The CQ bit was checked by efidler@blackberry.com

[commit-bot: I haz the power, 2014-02-06 13:55:25]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-02-06 13:55:25]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a lowly provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[efidler1, 2014-02-06 20:28:42]

looks like behdad's LGTM isn't enough for this.. can a "full committer" ptal?

BTW, the unprefixing patch is separate.

[eseidel, 2014-02-06 22:19:18]

eae is really your man, but lgtm.

[efidler1, 2014-02-06 22:59:39]

The CQ bit was checked by efidler@blackberry.com

[commit-bot: I haz the power, 2014-02-06 22:59:48]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/efidler@blackberry.com/77413003/220001

[commit-bot: I haz the power, 2014-02-07 01:03:49]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-02-07 01:03:49]

Retried try job too often on mac_blink_rel for step(s) webkit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_blink_...

[efidler1, 2014-02-07 18:38:12]

The CQ bit was checked by efidler@blackberry.com

[commit-bot: I haz the power, 2014-02-07 18:38:41]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/efidler@blackberry.com/77413003/220001

[efidler1, 2014-02-07 18:43:34]

The CQ bit was unchecked by efidler@blackberry.com

[efidler1, 2014-02-07 22:25:26]

The CQ bit was checked by efidler@blackberry.com

[commit-bot: I haz the power, 2014-02-07 22:25:52]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/efidler@blackberry.com/77413003/480001

[commit-bot: I haz the power, 2014-02-08 01:16:58]

Change committed as 166751

[eae, 2014-02-10 00:16:16]

LGTM post-facto