Move FontFaceSet.{check,load}'s argument default into IDL file

Move FontFaceSet.{check,load}'s argument default into IDL file

The default value of text parameter was handled in C++ code. Now the IDL
parser supports optional default value syntax, let's use it.

BUG=
TEST=fast/css/font*

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=181441

[Kunihiko Sakamoto, 2014-09-05 05:29:03]

ksakamoto@chromium.org changed reviewers:
+ bashi@chromium.org, tkent@chromium.org

[tkent, 2014-09-05 05:31:37]

The CQ bit was checked by tkent@chromium.org

[tkent, 2014-09-05 05:31:37]

lgtm

[commit-bot: I haz the power, 2014-09-05 05:32:01]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ksakamoto@chromium.org/540223002/1

[bashi, 2014-09-05 05:42:23]

LGTM

[commit-bot: I haz the power, 2014-09-05 06:00:34]

Committed patchset #1 (id:1) as 181441