This reverts commit 2af86102.

Reason for revert: 

Build bot is failing and this CL appears to be the reason.
https://ci.chromium.org/ui/p/chromium/builders/ci/linux-trusty-rel/20312/overview
https://bugs.chromium.org/p/chromium/issues/detail?id=1169629

Original change's description:
> Switch cc_unittests/viz_unittests to SwANGLE
>
> 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}

TBR=eugenis@chromium.org,sugoi@chromium.org,sugoi@google.com,kbr@chromium.org,weiliangc@chromium.org,jmadill@chromium.org,chromium-scoped@luci-project-accounts.iam.gserviceaccount.com

Change-Id: I114a082b893280b51279aebb51f621598064b733
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:1060139
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2643283Reviewed-by: Saurabh Nijhara <snijhara@google.com>
Commit-Queue: Saurabh Nijhara <snijhara@google.com>
Cr-Commit-Position: refs/heads/master@{#846051}