sync is a Python program that wraps
tools/git-sync-deps. Motivations for using it:
Written in Python, so it will work on all platforms.
Checks to see if the
DEPS file has changed since it last ran
gclient sync. If not, it skips that step.
sync is fast when it can do nothing, it is easy to do before every recompile of Skia. This is a good habit.