Please Valgrind by calling preConcat.

Please Valgrind by calling preConcat.

Valgrind's whining about m.setConcat(m, I).  That special cases into m =
m, which compiles into memcpy(&m, &m, sizeof(m)), and then Valgrind
decides that's not kosher because &m and &m overlap.  (memmove would
have been fine, but this is compiler generated code; not much we can do.)

preConcat gets us the same thing with an early can-we-noop check for I,
sidestepping the whole problem.

BUG=skia:

Committed: http://code.google.com/p/skia/source/detail?r=13972

[bsalomon, 2014-03-27 17:11:34]

lgtm

[mtklein, 2014-03-27 17:12:51]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-03-27 17:12:53]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/mtklein@chromium.org/214823003/1

[commit-bot: I haz the power, 2014-03-28 14:19:17]

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

[commit-bot: I haz the power, 2014-03-28 14:19:17]

Commit queue rejected this change because the description was changed
between the time the change entered the commit queue and the time it
was ready to commit. You can safely check the commit box again.

[mtklein, 2014-03-28 14:29:00]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-03-28 14:29:10]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/mtklein@chromium.org/214823003/1

[commit-bot: I haz the power, 2014-03-28 14:29:25]

Change committed as 13972