[ChromeDriver] Handle timeouts in session capabilities

Handle timeouts in session capabilities, according to W3C spec.

Bug: chromedriver:1997
Change-Id: Ie0c4bb8add482fa175f3bfe40210cf9fb0077001
Reviewed-on: https://chromium-review.googlesource.com/1243576
Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594097}
7 files changed