Remove PrerenderBrowserTest.PrerenderVisibility

The test legitimately fails when "prerender" value gets removed from
visibilityState as it is done in http://crrev.com/c/1356120

Unblock this change by removing the test. Traditional prerenders should
no longer happen, while nostate-prefetch should not ever look at
visibility state.

TBR=mattcary@chromium.org

Bug: 908582, 755921
Change-Id: I44da809f924b2730ac2b00fd85a1d1e484a3aacb
Reviewed-on: https://chromium-review.googlesource.com/c/1356939
Reviewed-by: Egor Pasko <pasko@chromium.org>
Commit-Queue: Egor Pasko <pasko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612792}
3 files changed