Reason for reland:
- content_browsertests and component_browsertests updated to
clear the correct private data directory between test runs.

Uses delete_device_stale=True when pushing. This will prevent tests
mistakenly passing when they depend on stale data files from a previous test.

TBR=jbudorick@chromium.org,thakis@chromium.org,mef@chromium.org,torne@chromium.org
BUG=607169,617213,616155

Review-Url: https://codereview.chromium.org/2043803003
Cr-Commit-Position: refs/heads/master@{#398601}