Use isolatestorage.Storage class in swarming.py instead of url_open calls.

That way swarming.py uses same isolate server protocol as the rest of the
code.

BUG=

Review URL: https://codereview.chromium.org/26124006

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/swarm_client@228254 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed