Mark SkPaths created by GrContext fallback draw logic as volatile

Mark SkPaths created by GrContext fallback draw logic as volatile

GrContext draw functions (drawRect, drawRRect,...) fall back to
GrContext::drawPath for complex cases. Mark the argument SkPath
as volatile, since it is.

Progressions for nvprmsaa:
          tabl_androidpolice.skp_1	11.6ms -> 10.3ms	0.89x
                desk_twitter.skp_1	9.21ms -> 8.08ms	0.88x
                tabl_sahadan.skp_1	8.97ms -> 7.65ms	0.85x
              desk_wikipedia.skp_1	5.63ms ->  4.5ms	0.8x
                desk_booking.skp_1	11.5ms -> 8.87ms	0.77x
                   desk_ebay.skp_1	   7ms -> 5.37ms	0.77x

Makes rrects and rects go to "simple path" path cache (cached by contents).

No change for msaa, gpu.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/806236e7974e8d05feecb8264eb361759f9db536

[Kimmo Kinnunen, 2015-05-21 13:03:30]

kkinnunen@nvidia.com changed reviewers:
+ bsalomon@google.com, jvanverth@google.com

[bsalomon, 2015-05-21 14:28:35]

lgtm

[Kimmo Kinnunen, 2015-05-22 05:39:41]

The CQ bit was checked by kkinnunen@nvidia.com

[commit-bot: I haz the power, 2015-05-22 05:39:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1150993002/20001

[commit-bot: I haz the power, 2015-05-22 05:45:59]

Committed patchset #2 (id:20001) as
https://skia.googlesource.com/skia/+/806236e7974e8d05feecb8264eb361759f9db536