Suppress flaky tests on macOS 10.13.6 with AMD GPUs.

WebGL conformance suppressions:
  conformance2/textures/misc/tex-mipmap-levels.html
  conformance2/textures/misc/tex-base-level-bug.html

Pixel test suppressions:
  Pixel_CSSFilterEffects
  Pixel_WebGLSadCanvas

Tbr: ynovikov@chromium.org
Bug: 870856, 872423
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I1420fe20b7a64bb40f3ba0209fd9bb08b3213b14
Reviewed-on: https://chromium-review.googlesource.com/1168470Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581958}

content/test/gpu/gpu_tests/pixel_expectations.py

@@ -55,6 +55,9 @@ class PixelExpectations(GpuTestExpectations):
     self.Fail('Pixel_CSSFilterEffects',
         ['mac', ('nvidia', 0xfe9)], bug=690277)
 
+    # Became flaky on 10.13.6.
+    self.Flaky('Pixel_CSSFilterEffects', ['highsierra', 'amd'], bug=872423)
+
     # TODO(kbr): flakily timing out on this configuration.
     self.Flaky('*', ['linux', 'intel', 'debug'], bug=648369)
 
@@ -109,7 +112,8 @@ class PixelExpectations(GpuTestExpectations):
     self.Fail('Pixel_WorkerRAF_OOPD', ['mac'], bug=851213)
 
     # TODO(kbr): temporary suppression for new test.
-    self.Flaky('Pixel_WebGLSadCanvas', ['linux', 'mac', 'win'], bug=575305)
+    self.Flaky('Pixel_WebGLSadCanvas', ['linux', 'win'], bug=575305)
+    self.Fail('Pixel_WebGLSadCanvas', ['mac'], bug=872423)
     self.Fail('Pixel_WebGLSadCanvas', ['android'], bug=575305)
 
     # Flaky on Android: crbug.com/860548

content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

@@ -434,9 +434,9 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
 
     # Regressions in 10.12.4.
     self.Fail('conformance2/textures/misc/tex-base-level-bug.html',
-        ['sierra'], bug=705865)
+        ['sierra', 'intel'], bug=705865)
     self.Fail('conformance2/textures/misc/tex-mipmap-levels.html',
-        ['sierra'], bug=705865)
+        ['sierra', 'intel'], bug=705865)
 
     # Regressions in 10.13
     self.Fail('deqp/functional/gles3/fbocolorbuffer/tex2d_00.html',
@@ -648,6 +648,13 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
     #     ['mac', 'amd'], bug=735483)
     # self.Fail('conformance2/rendering/texture-switch-performance.html',
     #     ['mac', 'amd'], bug=735483)
+
+    # The following two flaky failures are regressions in 10.13.6
+    # specifically.
+    self.Flaky('conformance2/textures/misc/tex-mipmap-levels.html',
+        ['mac', 'amd'], bug=870856)
+    self.Flaky('conformance2/textures/misc/tex-base-level-bug.html',
+        ['mac', 'amd'], bug=870856)
     self.Fail('deqp/functional/gles3/shaderoperator/common_functions.html',
         ['mac', 'amd'], bug=820225)
     self.Fail('deqp/functional/gles3/transformfeedback/' +