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:

Review URL: https://codereview.chromium.org/1150993002
2 files changed