Resolve "$ref" attributes in JSON schemas.

This allows managed extensions to declare policies that have a recursive type
(e.g. a hierarchy of bookmarks with folders) or to reuse the same policy type
for multiple policies.

BUG=108992

Review URL: https://codereview.chromium.org/88573002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237814 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237814
[Telemetry] Refactor common Android test harness functions.

This is a reland of crrev.com/62953024 which was reverted because
it broke other platforms.

Refactoring common cleanup code required by both
android_browser_finder.py and perf/setup.py and moving it into
pyblib/utils/test_environment.py.
Also, this change avoids killing twice the adb server when running
in a bot environment, where the adb restart is already invoked by
the bot steps.

BUG=268450
R=bulach@chromium.org,tonyg@chromium.org

Review URL: https://codereview.chromium.org/94683002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237815 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237815