Revert of Disable flaky ContinueWhereILeftOffTest.SessionStorage/SessionCookies tests (patchset #1 id:1 of https://codereview.chromium.org/2750783002/ )

Reason for revert:
Re-enabling the tests to see if the issue was fixed or get a call stack if it wasn't. See https://bugs.chromium.org/p/chromium/issues/detail?id=700696#c6

Original issue's description:
> Disable flaky ContinueWhereILeftOffTest.SessionStorage/SessionCookies tests
>
> They are flaky.
>
> BUG=700696, 700699
> TBR=sky@chromium.org
>
> Review-Url: https://codereview.chromium.org/2750783002
> Cr-Commit-Position: refs/heads/master@{#456659}
> Committed: https://chromium.googlesource.com/chromium/src/+/008c85e4011f9a860f94df75c3bd69c7aece6bab

TBR=yoichio@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=700696, 700699

Review-Url: https://codereview.chromium.org/2892063002
Cr-Commit-Position: refs/heads/master@{#473168}
1 file changed