Suppress a flaky WebGL2 test on Mac Intel

conformance/textures/canvas/tex-2d-rgba-rgba-unsigned_short_4_4_4_4.html

TBR=kbr

Bug: 1039465
Change-Id: Ie2b16100678c85986ca4a7006ac89f2cc552e558
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1988928Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#728799}

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

@@ -555,6 +555,7 @@ crbug.com/665197 [ mac intel-0xa2e ] conformance2/textures/image_bitmap_from_can
 crbug.com/658930 [ mac intel ] conformance2/textures/misc/integer-cubemap-texture-sampling.html [ Failure ]
 crbug.com/731877 [ mac intel-0xa2e no-passthrough ] conformance2/renderbuffers/multisampled-depth-renderbuffer-initialization.html [ Failure ]
 crbug.com/782317 [ mac intel ] conformance/rendering/rendering-stencil-large-viewport.html [ Failure ]
+crbug.com/1039465 [ mac intel ] conformance/textures/canvas/tex-2d-rgba-rgba-unsigned_short_4_4_4_4.html [ RetryOnFailure ]
 
 # Mac Passthrough
 crbug.com/982294 [ mac passthrough ] conformance/rendering/negative-one-index.html [ Failure ]