Add mode validation to PtProcRec::init.

Add mode validation to PtProcRec::init.

BUG=486946
Committed: https://skia.googlesource.com/skia/+/3ece53ed30b934894c87c8adb2a77cfdf2ecfcfe

[Oliver Chang, 2015-05-19 00:40:38]

ochang@chromium.org changed reviewers:
+ reed@chromium.org, senorblanco@chromium.org, sugoi@chromium.org

[reed1, 2015-05-19 12:41:02]

reed@google.com changed reviewers:
+ reed@google.com

[reed1, 2015-05-19 12:41:02]

What is a good way to test this sort of check? Should it be here or in a
different place/level?

[Oliver Chang, 2015-05-19 18:02:35]

On 2015/05/19 12:41:02, reed1 wrote:
> What is a good way to test this sort of check? Should it be here or in a
> different place/level?

I'm not familiar with skia testing, but I think in this case we should test
specifically that PtProcRec::init rejects invalid modes. Testing elsewhere would
not be completely reliable since this is used to index into function pointers
which are then called, taking execution to weird states.

Where would be a good place to add this? Taking a quick look at tests/ I don't
see anything that specifically tests this part of the code?

[Oliver Chang, 2015-05-21 19:47:01]

On 2015/05/19 18:02:35, ochang wrote:
> On 2015/05/19 12:41:02, reed1 wrote:
> > What is a good way to test this sort of check? Should it be here or in a
> > different place/level?
> 
> I'm not familiar with skia testing, but I think in this case we should test
> specifically that PtProcRec::init rejects invalid modes. Testing elsewhere
would
> not be completely reliable since this is used to index into function pointers
> which are then called, taking execution to weird states.
> 
> Where would be a good place to add this? Taking a quick look at tests/ I don't
> see anything that specifically tests this part of the code?

Although this should no longer be hit by mtklein@'s patch, is it still worth
adding this check?

[reed1, 2015-05-21 21:20:39]

The CQ bit was checked by reed@google.com

[reed1, 2015-05-21 21:20:40]

lgtm

[commit-bot: I haz the power, 2015-05-21 21:21:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1142563003/20001

[commit-bot: I haz the power, 2015-05-21 22:44:57]

Committed patchset #2 (id:20001) as
https://skia.googlesource.com/skia/+/3ece53ed30b934894c87c8adb2a77cfdf2ecfcfe