Suppress WebGL S3TC extension flakes on Win/NVIDIA/OpenGL/passthrough.

The following two tests are observed to flake in
webgl2_conformance_gl_passthrough_tests :

  conformance/extensions/webgl-compressed-texture-s3tc.html
  conformance/extensions/webgl-compressed-texture-s3tc-srgb.html

Bug: 963205
Change-Id: Ic9c8ae5b7099f5fc02d7ccab802edbcb912c0939
Tbr: jonross@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1636229Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664540}

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

@@ -118,6 +118,8 @@ crbug.com/728670 [ d3d11 win nvidia-0x1cb3 ] conformance2/textures/image_bitmap_
 crbug.com/782254 [ d3d11 win nvidia-0x1cb3 ] conformance2/rendering/attrib-type-match.html [ RetryOnFailure ]
 
 # WIN / OpenGL / NVIDIA failures
+crbug.com/963205 [ win nvidia opengl passthrough ] conformance/extensions/webgl-compressed-texture-s3tc.html [ RetryOnFailure ]
+crbug.com/963205 [ win nvidia opengl passthrough ] conformance/extensions/webgl-compressed-texture-s3tc-srgb.html [ RetryOnFailure ]
 crbug.com/715001 [ opengl win nvidia                    ] conformance/limits/gl-max-texture-dimensions.html [ Failure ]
 crbug.com/703779 [ opengl win nvidia                    ] conformance/textures/misc/texture-size.html [ Failure ]
 crbug.com/830046 [ opengl win passthrough nvidia        ] conformance2/rendering/blitframebuffer-size-overflow.html [ Skip ]

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

@@ -210,6 +210,8 @@ crbug.com/956134 [ win d3d9 ] conformance/extensions/webgl-depth-texture.html [
 # WIN / OpenGL / NVIDIA failures
 crbug.com/715001 [ win nvidia opengl passthrough ] conformance/limits/gl-max-texture-dimensions.html [ Failure ]
 crbug.com/703779 [ win nvidia opengl ] conformance/textures/misc/texture-size.html [ Failure ]
+crbug.com/963205 [ win nvidia opengl passthrough ] conformance/extensions/webgl-compressed-texture-s3tc.html [ RetryOnFailure ]
+crbug.com/963205 [ win nvidia opengl passthrough ] conformance/extensions/webgl-compressed-texture-s3tc-srgb.html [ RetryOnFailure ]
 
 # Mark ANGLE's OpenGL as flaky on Windows Nvidia
 crbug.com/582083 [ win nvidia opengl ] conformance/* [ RetryOnFailure ]