Add a simple tool for isolating a path from an SKP

BUG=skia:

Change-Id: I5ca9bbd43919e3f65ea940847c68f85cc78dfeda
Reviewed-on: https://skia-review.googlesource.com/10130
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
4 files changed