Add Unicode Variation Selector support to harfBuzzGetGlyph on Linux

Add Unicode Variation Selector support to harfBuzzGetGlyph on Linux

Most of the work to support Unicode Variation Selector was done in a
separate CL[1], but it was not enabled for Linux due to crbug.com/462689.

With the bundled harfbuzz on Linux stabilized, this patch enables the
Unicode Variation Selector support on Linux.

[1] https://codereview.chromium.org/1149693002

BUG=383580
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198565

[kojii, 2015-07-08 08:46:48]

kojii@chromium.org changed reviewers:
+ behdad@google.com, drott@chromium.org, eae@chromium.org

[kojii, 2015-07-08 08:46:48]

PTAL.

[eae, 2015-07-08 14:25:25]

LGTM

[kojii, 2015-07-09 05:25:21]

The CQ bit was checked by kojii@chromium.org

[commit-bot: I haz the power, 2015-07-09 05:25:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1209043010/20001

[commit-bot: I haz the power, 2015-07-09 05:29:16]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=198565

[jbroman, 2015-07-09 15:48:10]

A revert of this CL (patchset #2 id:20001) has been created in
https://codereview.chromium.org/1229923003/ by jbroman@chromium.org.

The reason for reverting is: Breaks chromeos=1 builds on Linux.

../../third_party/WebKit/Source/platform/fonts/shaping/HarfBuzzFace.cpp:201:13:
error: use of undeclared identifier 'hb_ot_font_set_funcs'
            hb_ot_font_set_funcs(hbFontData->m_hbOpenTypeFont);
            ^
1 error generated.
.

[kojii, 2015-07-09 16:00:56]

From the IRC as a record for investigations:

use_goma=1 chromeos=1 clang=1 clang_use_chrome_plugins=1
libharfbuzz-dev version: 0.9.27-1ubuntu1

use_system_harfbuzz=0 gives me a longer list of warnings over hidden symbols,
which are being treated as errors. http://pastebin.com/5Up4nyBv