Refactor OverlayTest to make it easier to test additional strategies.

Refactor OverlayTest to make it easier to test additional strategies.

Refactor to remove code duplication between OverlayTest and SandwichTest.
This is to make it easier to add tests for new strategies, such as the upcoming AllOrNothing strategy.

CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Committed: https://crrev.com/e34f77dea96ba7d862d1631e7490a102a698cd4f
Cr-Commit-Position: refs/heads/master@{#351392}

[Andre, 2015-09-29 20:26:45]

andresantoso@chromium.org changed reviewers:
+ ccameron@chromium.org

[Andre, 2015-09-29 20:26:45]

ccameron PTAL.

[ccameron, 2015-09-29 20:37:30]

Much better. lgtm

[Andre, 2015-09-29 20:38:03]

The CQ bit was checked by andresantoso@chromium.org

[commit-bot: I haz the power, 2015-09-29 20:39:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1372873004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1372873004/1

[commit-bot: I haz the power, 2015-09-29 20:46:00]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-29 20:47:18]

Patchset 1 (id:??) landed as
https://crrev.com/e34f77dea96ba7d862d1631e7490a102a698cd4f
Cr-Commit-Position: refs/heads/master@{#351392}