Suppress further flake on Mac NVIDIA.

conformance/ogles/GL/exp2/exp2_001_to_008.html is flaking in the WebGL
2.0 suite as well, not just the WebGL 1.0 suite.

Tbr: senorblanco@chromium.org
Bug: 923080
Change-Id: I9aef3e7035d82f66e84ed76d1a93697329f3225b
Reviewed-on: https://chromium-review.googlesource.com/c/1441471Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#626882}

content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

@@ -492,6 +492,8 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
     self.Flaky(
         'conformance/extensions/webgl-compressed-texture-size-limit.html',
         ['mac', ('nvidia', 0xfe9)], bug=483282)
+    self.Flaky('conformance/ogles/GL/exp2/exp2_001_to_008.html',
+        ['mac', ('nvidia', 0xfe9)], bug=923080)
     self.Fail('conformance/programs/' +
         'gl-bind-attrib-location-long-names-test.html',
         ['mac', ('nvidia', 0xfe9)], bug=483282)