Small pathops cleanup.

Newer clang compiler produces the diagnostic

../../tests/PathOpsDebug.cpp:1349:44:
error: comparison of unsigned enum expression >= 0 is always true
[-Werror,-Wtautological-unsigned-enum-zero-compare]
        if (!firstOp && c->operand() && op >= 0) {

The check seems to be defending against bad values of SkPathOp, but
this now seems unnecessary. This also adds 'rdiff' to kPathOpStr for
future debugging.

Change-Id: I08e5ba77c56e519ce4d9ae89491f7ccd5eb7f944
Reviewed-on: https://skia-review.googlesource.com/57104
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
2 files changed