Handle deleting/downloading/uploading >=1M GS directories
Handle deleting/downloading/uploading >=1M GS directories

BUG=skia:5425

Review-Url: https://codereview.chromium.org/2072773002

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot