Pre-clamp path tolerance

Pre-clamp path tolerance

GrDefaultPathRenderer was using GrPathUtils::worstCasePointCount, which
clamped the tolerance. Then it built geometry with the unclamped value,
leading to vertex overflow (found by canvas fuzzer). The new rule is if
you use GrPathUtils, your tolerance must come from scaleToleranceToSrc.

Bug: skia:6569
Change-Id: I851519db8e569e570c717033d697f3d4d3d787fb
Reviewed-on: https://skia-review.googlesource.com/16234
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>