Revert of Add test for ChromeVox keyboard commands. (patchset #21 id:390004 of https://codereview.chromium.org/490443002/)

Reason for revert:
flakes, see http://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%281%29/builds/31850

failures:
TestAsNormalAndGuestUser/SpokenFeedbackTest.ChromeVoxPrefixKey/0
TestAsNormalAndGuestUser/SpokenFeedbackTest.ChromeVoxPrefixKey/1
TestAsNormalAndGuestUser/SpokenFeedbackTest.ChromeVoxShiftSearch/1
TestAsNormalAndGuestUser/SpokenFeedbackTest.ChromeVoxShiftSearch/0
LoggedInSpokenFeedbackTest.AddBookmark

Original issue's description:
> Add test for ChromeVox keyboard commands.
>
> This is just a couple of quick sanity checks to prevent future regressions
> like the one in the linked bug. It tests both a Search+Shift shortcut and
> the corresponding Prefix Key shortcut.
>
> Adds support for sending the meta modifier key in
> aura/x11 tests.
>
> BUG=404470
>
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=291547
>
> Committed: https://chromium.googlesource.com/chromium/src/+/8cab2737f1cb6e6011b0946f6bef5027868602c0
>
> Committed: https://crrev.com/91703961c10dfa0f452999ed7cb87945ea817362
> Cr-Commit-Position: refs/heads/master@{#293687}
>
> Committed: https://crrev.com/15ea141544fedaf306c94890b5be19b7c5df885a
> Cr-Commit-Position: refs/heads/master@{#296074}

TBR=dtseng@chromium.org,sky@chromium.org,dmazzoni@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=404470

Review URL: https://codereview.chromium.org/603823002

Cr-Commit-Position: refs/heads/master@{#296627}
2 files changed