Fix font instantiation assertion failure on session restore

Fix font instantiation assertion failure on session restore

It seems in certain cases font fallback returns a fontconfig interface
id which can then later not be reused by Skia. This patch fixes an
incorrect fallback to using the family in that case and returns a nullptr
instead, which fixes the assertion failure. However, we need to
investigate why the Skia typeface creation with the returned
fciId is unsuccessful, filed crbug.com/403348 for this remaining question.

BUG=273261
R=eae,eseidel

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=180214

[eae, 2014-08-13 16:05:26]

LGTM

[Dominik Röttsches, 2014-08-13 16:54:26]

On 2014/08/13 16:05:26, eae wrote:
> LGTM

Thanks - I think this should eventually land, but unfortunately, bug 273261 is
not fixed - it is still reproducible even with this change. :-( - I am checking.

[Dominik Röttsches, 2014-08-13 18:06:47]

The CQ bit was checked by dominik.rottsches@intel.com

[commit-bot: I haz the power, 2014-08-13 18:07:25]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dominik.rottsches@intel.com/470493003/1

[commit-bot: I haz the power, 2014-08-13 19:44:43]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/22601)

[commit-bot: I haz the power, 2014-08-13 20:54:02]

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

[commit-bot: I haz the power, 2014-08-13 20:54:05]

Try jobs failed on following builders:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/22619)

[Dominik Röttsches, 2014-08-13 21:53:37]

The CQ bit was checked by dominik.rottsches@intel.com

[commit-bot: I haz the power, 2014-08-13 21:54:15]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dominik.rottsches@intel.com/470493003/1

[commit-bot: I haz the power, 2014-08-13 23:10:37]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/22640)

[commit-bot: I haz the power, 2014-08-14 00:03:04]

Committed patchset #1 (1) as 180214