Adding a performance test for font fallback

Adding a performance test for font fallback

Using a set of ~19000 characters extracted from DRT's font configuration, the
test is slicing them into smaller sets and rendering them in a page.  This
exercises WebFontInfo::fallbackFontForChar which is the cause for slowness,
as described in bug 266214.
This test case is preparation for landing the an optimization patch which
drastically reduces the number of fontconfig calls in the sandbox IPC process.

BUG=266214
R=eseidel,eae

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=177337

[Dominik Röttsches, 2014-07-01 20:29:25]

Using this test case, we can measure the cold start improvements of
https://codereview.chromium.org/342823005/ quite well.

Before:  2082.52ms ± 1.92%	
After:   170.58ms ± 4.36%

[eae, 2014-07-01 20:49:42]

LGTM

[Dominik Röttsches, 2014-07-01 21:17:20]

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

[commit-bot: I haz the power, 2014-07-01 21:17:46]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dominik.rottsches@intel.com/360363002/1

[commit-bot: I haz the power, 2014-07-01 22:21:13]

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/14926)

[commit-bot: I haz the power, 2014-07-01 23:53:26]

Change committed as 177337