[ChromeDriver] Fixes for pause actions

Fix a bug in the processing of pause subtype of key actions, as reported
by james.h.evans.jr@gmail.com. Also factor out code that processes pause
actions to ensure consistency.

Bug: chromedriver:1897
Change-Id: I68af8f7025dc344683554f9954576a0ac568e4d7
Reviewed-on: https://chromium-review.googlesource.com/c/1376108
Reviewed-by: Lan Wei <lanwei@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616400}
1 file changed