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Right now some tests depend on previous tests' global states setting
to be able to run correctly.

This CL is set these states correctly for these tests so they can run
independently from previous tests.

BUG=968345
TEST=gl_unittests with --gtest_filter=SkipVideoLayerEmptyContentsRect|NV12SwapChain
R=sunnyps@chromium.org

Change-Id: I535b70065971e2803a09c1cedf7e243a4df6ace5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1633534
Commit-Queue: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Sunny Sachanandani <sunnyps@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664640}