Re-enable a context lost test on Mac.

GpuCrash_GPUProcessCrashesExactlyOncePerVisitToAboutGpuCrash should no
longer be flaky, at least not for the previous reason.

Bug: 861956
Tbr: bsalomon@google.com
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: I37a34caf9b5725ddc877ac81a1760ad72dfbb261
Reviewed-on: https://chromium-review.googlesource.com/1142233
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576176}

content/test/gpu/gpu_tests/context_lost_expectations.py

@@ -42,12 +42,6 @@ class ContextLostExpectations(GpuTestExpectations):
     self.Skip('ContextLost_WebGLContextLostFromSelectElement',
               ['lion', 'debug'], bug=498149)
 
-    # There are probably multiple race conditions in the renderer
-    # process related to context loss, but they're happening most
-    # often on the Mac bots.
-    self.Flaky('GpuCrash_GPUProcessCrashesExactlyOncePerVisitToAboutGpuCrash',
-               ['mac'], bug=861956)
-
     # 'Browser must support tab control' raised on Android
     self.Skip('GpuCrash_GPUProcessCrashesExactlyOncePerVisitToAboutGpuCrash',
               ['android'], bug=609629)