Add blanket GPU Kevin expectation

We continue to have random flakes in numerous tests on ChromeOS Kevin
devices seemingly due to a driver issue, so mark every test as
RetryOnFailure.

Bug: 1091562
Change-Id: I60995bb434159f1daa002f889a13462621d448c5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2457886
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Auto-Submit: Brian Sheedy <bsheedy@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814831}

content/test/gpu/gpu_tests/test_expectations/webgl_conformance_expectations.txt

@@ -766,6 +766,9 @@ crbug.com/1080397 [ chromeos-board-kevin ] conformance/textures/video/tex-2d-rgb
 crbug.com/1080397 [ chromeos-board-kevin ] conformance/textures/video/tex-2d-rgb-rgb-unsigned_short_5_6_5.html [ Failure ]
 crbug.com/1108368 [ chromeos-board-kevin ] conformance/misc/shader-precision-format.html [ Failure ]
 
+# Flaky renderer hangs suspected due to some driver issue on Kevin devices.
+crbug.com/1091562 [ chromeos-board-kevin ] * [ RetryOnFailure ]
+
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 # SwiftShader failures #
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