[ChromeDriver] Key type actions for the actions API

This CL contains the key type actions. Follow up CLs for tests and
pointer/pause actions

spec: https://w3c.github.io/webdriver/webdriver-spec.html#actions

Bug: chromedriver:1897
Change-Id: I135df58d97a45494e51a5ac09dfce021f7d094d3
Reviewed-on: https://chromium-review.googlesource.com/692599
Commit-Queue: Jonathon Kereliuk <kereliuk@chromium.org>
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#508958}
5 files changed