Do not return error from ChromeEarlGrey methods.

ChromeEarlGrey fails on error and callers of ChromeEarlGrey methods do
not expect NSError returns anymore.

Also removed block of code from testShowHeaderWhenChildTabCloses, which
can no longer be reached (because tapWebStateElementWithID asserts inside).

Bug: 963613
Change-Id: I79ad041857599f17481269eeb6c62b4f04693683
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1658930
Commit-Queue: Eugene But <eugenebut@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#669413}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: b3ca389a409c468eb568ee025dcfac3b3081c5ba
3 files changed