This cl changes the software backend used for
running viz_unittests and cc_unittests from
SwiftShader GL to SwANGLE (ANGLE on SwiftShader
Vulkan). Other tests suites may be affected.

From this cl, performance expectations for test
runs will likely change. For example, cc_unittests
appears to run faster, while viz_unittests and
views_unittests appear to run slower. Note that
this is still using the validating command decoder,
and once the OOP Raster tests can run on the
passthrough command decoder, we'll be able to use
it and gain some performance on all these test runs.

TBR=kbr@chromium.org
TBR=weiliangc@chromium.org
TBR=eugenis@chromium.org
Reason for TBR: These changes were already reviewed here https://chromium-review.googlesource.com/c/chromium/src/+/2532042

Bug: chromium:1060139
Change-Id: Idb0048d3a8e0dfe6855e1700ed26fb076be0c4f1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2580360
Commit-Queue: Alexis Hétu <sugoi@chromium.org>
Reviewed-by: Evgenii Stepanov <eugenis@chromium.org>
Reviewed-by: Alexis Hétu <sugoi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845826}