This reverts commit fad918f8.

Reason for revert: attempt to fix anglebug.com/2537

Original change's description:
> ANGLETest: Reuse test windows per-renderer
> 
> When running angle_end2end_tests unfiltered with the OpenGL and Vulkan
> backends enabled, the test window was recreated all the time and grabbed
> focus every-time it was created. This made it impossible to do anything
> with the machine running the tests.
> 
> Fix this by having one OSWindow per renderer group that's lazily created:
> this solves most of the issue since only a couple windows end up being
> created, and at the beginning of the test suite.
> 
> BUG=
> 
> Change-Id: I7a51300f0d59d8b6bb79e54d20b3acbf01068002
> Reviewed-on: https://chromium-review.googlesource.com/1038433
> Commit-Queue: Corentin Wallez <cwallez@chromium.org>
> Reviewed-by: Jamie Madill <jmadill@chromium.org>

TBR=geofflang@chromium.org,jmadill@chromium.org,cwallez@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I93bdfa38757cbe2a6ce939c0c3e3da806307e7dd
Reviewed-on: https://chromium-review.googlesource.com/1050326Reviewed-by: Frank Henigman <fjhenigman@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Frank Henigman <fjhenigman@chromium.org>