Mark deqp/functional/gles3/shaderloop_while.html as flaky

This test has begun flaking regularly on Windows. Marking as
RetryOnFailure so that we can hopefully handle the flakes.

This is a follow up to https://chromium-review.googlesource.com/c/chromium/src/+/2096089
Where we marked deqp/functional/gles3/shaderloop_do_while.html as flaky.
Seems both related tests are affected.

TBR=ynovikov@chromium.org
TEST=  webgl2_conformance_gl_passthrough_tests
       deqp/functional/gles3/shaderloop_while.html
Bug: 1060024

Change-Id: Ie9b6e1f5b56a5d1e6515baff0f5133e09cc2e45c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2094740Reviewed-by: Jonathan Ross <jonross@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748923}

content/test/gpu/gpu_tests/test_expectations/webgl2_conformance_expectations.txt

@@ -215,6 +215,7 @@ crbug.com/887578 [ opengl win passthrough nvidia        ] deqp/data/gles3/shader
 crbug.com/965648 [ opengl win passthrough nvidia-0x1cb3 ] deqp/functional/gles3/shaderstruct.html [ RetryOnFailure ]
 crbug.com/822733 [ opengl win nvidia-0x1cb3             ] deqp/functional/gles3/transformfeedback/* [ RetryOnFailure ]
 crbug.com/1060024 [ opengl win passthrough nvidia-0x1cb3 ] deqp/functional/gles3/shaderloop_do_while.html [ RetryOnFailure ]
+crbug.com/1060024 [ opengl win passthrough nvidia-0x1cb3 ] deqp/functional/gles3/shaderloop_while.html [ RetryOnFailure ]
 
 # Win / AMD