Suppress failing webgl tests on SwANGLE/Mac/passthrough.

These tests began failing on Sep 21:
conformance/textures/misc/copy-tex-image-2d-formats.html
conformance/misc/uninitialized-test.html
conformance/textures/misc/copy-tex-image-and-sub-image-2d.html

Bug: chromium:1134756
Change-Id: I788ab772a1ee8c5159366404e37abc30a412744d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2446654
Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813401}

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

@@ -835,3 +835,7 @@ crbug.com/1099979 [ mac swiftshader passthrough ] conformance/textures/video/tex
 crbug.com/1099979 [ mac swiftshader passthrough ] conformance/textures/video/tex-2d-rgba-rgba-unsigned_short_4_4_4_4.html [ Failure ]
 crbug.com/1099979 [ mac swiftshader passthrough ] conformance/textures/video/tex-2d-rgba-rgba-unsigned_short_5_5_5_1.html [ Failure ]
 crbug.com/1099979 [ mac swiftshader passthrough ] conformance/textures/webgl_canvas/tex-2d-rgba-rgba-unsigned_short_5_5_5_1.html [ Failure ]
+
+crbug.com/1134756 [ mac swiftshader passthrough ] conformance/textures/misc/copy-tex-image-2d-formats.html [ Failure ]
+crbug.com/1134756 [ mac swiftshader passthrough ] conformance/misc/uninitialized-test.html [ Failure ]
+crbug.com/1134756 [ mac swiftshader passthrough ] conformance/textures/misc/copy-tex-image-and-sub-image-2d.html [ Failure ]