trivial fix for TextBlobCache

trivial fix for TextBlobCache

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/f6e97e6f62c08042886dc50850c1d8c929418602

[joshualitt, 2015-04-10 14:11:20]

joshualitt@google.com changed reviewers:
+ robertphillips@google.com

[joshualitt, 2015-04-10 14:11:44]

joshualitt@google.com changed reviewers:
- robertphillips@google.com

[joshualitt, 2015-04-10 14:12:01]

joshualitt@google.com changed reviewers:
+ robertphillips@google.com

[joshualitt, 2015-04-10 14:12:06]

The CQ bit was checked by joshualitt@google.com

[commit-bot: I haz the power, 2015-04-10 14:12:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1076193003/1

[commit-bot: I haz the power, 2015-04-10 14:12:23]

Note for Reviewers:
The CQ is waiting for an approval.
If you believe that the CL is not ready yet, or if you would like to L-G-T-M
with comments then please uncheck the CQ checkbox.

Waiting for LGTM from valid reviewer(s) till 2015-04-10 20:12 UTC

[joshualitt, 2015-04-10 14:12:34]

Whoops, missed this on the last CL.  It won't cause a segfault but it will cause
unnecessary flushing

[robertphillips, 2015-04-10 14:14:47]

lgtm

[commit-bot: I haz the power, 2015-04-10 14:23:34]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/f6e97e6f62c08042886dc50850c1d8c929418602