Make SkNWayCanvas use conservative clipping.

Like most other canvas subclasses, its clips don't need to be perfect.

BUG=chromium:668925

Change-Id: I107f8ed6fa60654426fd52c066b1018d5801850d
Reviewed-on: https://skia-review.googlesource.com/5308
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Mike Reed <reed@google.com>
3 files changed