Suppress tex-2d-rgb16f-rgb-half_float on macOS.

conformance2/textures/canvas/tex-2d-rgb16f-rgb-half_float.html has
become flaky, reporting an error in SharedImageStub with subsequent
context loss.

Bug: 965209
Change-Id: I3e7e5e2f456d0bbf1b5f87cf5cc78511131e1083
Tbr: geofflang@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1620699
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661491}
diff --git a/content/test/gpu/gpu_tests/test_expectations/webgl2_conformance_expectations.txt b/content/test/gpu/gpu_tests/test_expectations/webgl2_conformance_expectations.txt
index 59f9fa1..217b1c9 100644
--- a/content/test/gpu/gpu_tests/test_expectations/webgl2_conformance_expectations.txt
+++ b/content/test/gpu/gpu_tests/test_expectations/webgl2_conformance_expectations.txt
@@ -311,6 +311,7 @@
 crbug.com/709351 [ mac ] conformance2/glsl3/vector-dynamic-indexing-swizzled-lvalue.html [ Failure ]
 crbug.com/630800 [ intel mac ] conformance2/rendering/framebuffer-completeness-unaffected.html [ Failure ]
 crbug.com/630800 [ nvidia mac ] conformance2/rendering/framebuffer-completeness-unaffected.html [ Failure ]
+crbug.com/965209 [ mac ] conformance2/textures/canvas/tex-2d-rgb16f-rgb-half_float.html [ RetryOnFailure ]
 crbug.com/630800 [ intel mac ] deqp/functional/gles3/fbocompleteness.html [ Failure ]
 crbug.com/630800 [ nvidia mac ] deqp/functional/gles3/fbocompleteness.html [ Failure ]
 crbug.com/811614 [ amd mac ] deqp/functional/gles3/negativeshaderapi.html [ Failure ]