Don't pass null to memcmp.

Don't pass null to memcmp.

This will allow us to add nonnull-attribute to the UBSAN bot.

We are in fact hitting a case where one of the arguments is null and the other
not, which seems dicey.  I think the scenario is comparing the empty pathref
with another path ref that's just been COWed, without any verbs or points yet.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/d4897591fddf8f2a4860066449fb7dd8b0cc7b77

[mtklein, 2014-11-14 17:04:02]

mtklein@google.com changed reviewers:
+ bsalomon@google.com, caryclark@google.com, mtklein@google.com, reed@google.com

[mtklein, 2014-11-14 17:04:42]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-11-14 17:04:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/732643002/60001

[commit-bot: I haz the power, 2014-11-14 17:04:59]

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 2014-11-14 23:04 UTC

[mtklein, 2014-11-14 17:06:30]

The CQ bit was unchecked by mtklein@google.com

[reed1, 2014-11-14 17:09:41]

lgtm w/ question about possibly simplifying/clarifying the check.

https://codereview.chromium.org/732643002/diff/60001/src/core/SkPathRef.cpp
File src/core/SkPathRef.cpp (right):

https://codereview.chromium.org/732643002/diff/60001/src/core/SkPathRef.cpp#n...
src/core/SkPathRef.cpp:196: if (ref.fVerbCnt == 0 && ref.fPointCnt == 0) {
is it enough to just check fVerbCnt (and if it is zero, assert that fPointCnt is
also zero)?

[mtklein, 2014-11-14 17:13:20]

https://codereview.chromium.org/732643002/diff/60001/src/core/SkPathRef.cpp
File src/core/SkPathRef.cpp (right):

https://codereview.chromium.org/732643002/diff/60001/src/core/SkPathRef.cpp#n...
src/core/SkPathRef.cpp:196: if (ref.fVerbCnt == 0 && ref.fPointCnt == 0) {
On 2014/11/14 17:09:41, reed1 wrote:
> is it enough to just check fVerbCnt (and if it is zero, assert that fPointCnt
is
> also zero)?

Yes (until we add pointless verbs :P).  Done.

[mtklein, 2014-11-14 17:13:44]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-11-14 17:14:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/732643002/80001

[commit-bot: I haz the power, 2014-11-14 17:22:44]

Committed patchset #5 (id:80001) as
https://skia.googlesource.com/skia/+/d4897591fddf8f2a4860066449fb7dd8b0cc7b77