Retry flaky conformance/context/context-size-change.html

This test has begun flaking since an Angle roll landed:
  https://chromium-review.googlesource.com/c/chromium/src/+/2330032/2
This change marks it as retry while the Angle team looks to revert
the cause.

TBR=ynovikov@chromium.org
TEST=webgl_conformance_vulkan_passthrough_tests on Intel GPU
     conformance/context/context-size-change.htm
Bug: 1111652


Change-Id: I78b442589af66fac14ebe6bdf1002d4e5f15d607
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2332836Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/master@{#793632}

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

@@ -379,6 +379,10 @@ crbug.com/1004581 [ win amd vulkan passthrough ] conformance/rendering/multisamp
 crbug.com/1010942 [ win amd vulkan passthrough ] conformance/glsl/samplers/glsl-function-texture2dproj.html [ Failure ]
 crbug.com/angleproject/4286 [ win amd vulkan passthrough ] conformance/rendering/out-of-bounds-array-buffers.html [ Failure ]
 
+# Vulkan / Win10 / Intel / Passthrough
+# Flaking since an identified Angle roll.
+crbug.com/1111652 [ win10 intel vulkan passthrough ] conformance/context/context-size-change.html [ RetryOnFailure ]
+
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 # Mac failures     #
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