Suppress shaderoperator flakes on Mac NVIDIA.

Mark these two tests as failing:
  deqp/functional/gles3/shaderoperator/binary_operator_01.html
  deqp/functional/gles3/shaderoperator/unary_operator_01.html

Bug: 756537
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: I08a3d1b7ba3e240aec2347a92e8b52156780c510
Tbr: rjkroege@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/1054773Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557746}

content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

@@ -602,9 +602,13 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
     self.Fail('conformance2/uniforms/draw-with-uniform-blocks.html',
         ['mac', ('nvidia', 0xfe9)], bug=795052)
 
-    # When this fails on this configuration, it fails multiple times in a row.
+    # When these fail on this configuration, they fail multiple times in a row.
+    self.Fail('deqp/functional/gles3/shaderoperator/binary_operator_01.html',
+        ['mac', 'nvidia'], bug=756537)
     self.Fail('deqp/functional/gles3/shaderoperator/common_functions.html',
         ['mac', 'nvidia'], bug=756537)
+    self.Fail('deqp/functional/gles3/shaderoperator/unary_operator_01.html',
+        ['mac', 'nvidia'], bug=756537)
 
     # Mac AMD
     # TODO(kbr): uncomment the following two exepectations after test