Add an assert that we still have a buffer to readFromBuffer().

Add an assert that we still have a buffer to readFromBuffer().

sk_free(fBuffer.detach()) means fBuffer will be left as NULL, not a zero-length malloc.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/1f66e4539177297545270ff3cbd1d8fa6c3481ac

[mtklein, 2014-10-20 23:17:37]

mtklein@google.com changed reviewers:
+ mtklein@google.com, scroggo@google.com

[mtklein, 2014-10-20 23:17:40]

The CQ bit was checked by mtklein@google.com

[mtklein, 2014-10-20 23:17:40]

The CQ bit was unchecked by mtklein@google.com

[mtklein, 2014-10-20 23:17:41]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-10-20 23:17:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/669813002/1

[commit-bot: I haz the power, 2014-10-20 23:17:50]

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 2014-10-21 05:17 UTC

[scroggo, 2014-10-20 23:21:40]

lgtm

[commit-bot: I haz the power, 2014-10-21 14:12:57]

Committed patchset #1 (id:1) as 1f66e4539177297545270ff3cbd1d8fa6c3481ac