create tools/tests/run_all.py to run all our Python self-tests within tools

Eventually, we want all of these self-tests to be written in Python;
this change makes it easier for us to add new Python self-tests, and discourages
the addition of bash self-tests.

BUG=skia:677,skia:1943
NOTRY=True
R=rmistry@google.com, scroggo@google.com

Author: epoger@google.com

Review URL: https://codereview.chromium.org/112163004

git-svn-id: http://skia.googlecode.com/svn/trunk@12775 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed