End to end cellular integration test.

Tests the following UI functionality with chrome.networkingPrivate APIs
- Tests that the device auto connects to cellular network.
- Tests that the device prefers ethernet over cellular network.
- Tests that the enabling and disabling of cellular modem works.

BUG=chromium:469950
TEST=Tested against a local DUT setup.

Change-Id: Icaecf6b713a8252e1e489d5ce17ca881951393c3
Reviewed-on: https://chromium-review.googlesource.com/292445
Commit-Ready: harpreet Grewal <harpreet@chromium.org>
Tested-by: harpreet Grewal <harpreet@chromium.org>
Reviewed-by: Prathmesh Prabhu <pprabhu@chromium.org>
Reviewed-by: harpreet Grewal <harpreet@chromium.org>
9 files changed