Expand WebGL2 test suppression

deqp/functional/gles3/shaderstruct.html
Flaky on Linux NVIDIA GL passthrough as well.

TBR=kbr

Bug: 965648
Change-Id: I6baa0c314a4aa2839cd9c9ae59470720cc7c5c43
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1819519Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699048}

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

@@ -274,6 +274,7 @@ crbug.com/angleproject/3742 [ opengl win passthrough ] conformance2/rendering/cl
 
 # Passthrough command decoder / Linux / OpenGL / NVIDIA
 crbug.com/766918 [ opengl linux passthrough nvidia ] conformance2/textures/image_bitmap_from_video/* [ RetryOnFailure ]
+crbug.com/965648 [ opengl linux passthrough nvidia ] deqp/functional/gles3/shaderstruct.html [ RetryOnFailure ]
 
 
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