Mark texture-sub-image-cube-maps.html as Retry

Recently there has been flaky texture errors on Win7 AMD.
This marks the flaking test as RetryOnFailure to help the tree, until
the root cause can be investigated

TBR=ynovikov@chromium.org
TEST= webgl2_conformance_d3d11_passthrough_tests
conformance/textures/misc/texture-sub-image-cube-maps.html
Bug: 1110951

Change-Id: Ifbdfe117af7cc8981743a12109db6da71014f915
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2330070Reviewed-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@{#793255}

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

@@ -286,6 +286,9 @@ crbug.com/angleproject/2424 [ d3d11 win amd ] deqp/functional/gles3/texturespeci
 crbug.com/angleproject/2424 [ d3d11 win amd ] deqp/functional/gles3/texturespecification/teximage3d_unpack_params.html [ Failure ]
 crbug.com/angleproject/2424 [ d3d11 win amd ] deqp/functional/gles3/texturespecification/texsubimage3d_unpack_params.html [ Failure ]
 
+# AMD texture handling has become flaky.
+crbug.com/1110951 [ d3d11 win amd ] conformance/textures/misc/texture-sub-image-cube-maps.html [ RetryOnFailure ]
+
 # Have seen this time out. Think it may be because it's currently
 # the first test that runs in the shard, and the browser might not
 # be coming up correctly.