Revert "Mark a context_lost test Flaky"

The underlying issue has been fixed.

Bug: 762745
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I9899e66b3ed149aeec086ee0ce41ad4f07f1cadc
Reviewed-on: https://chromium-review.googlesource.com/683244Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Antoine Labour <piman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#504239}

content/test/gpu/gpu_tests/context_lost_expectations.py

@@ -39,10 +39,6 @@ class ContextLostExpectations(GpuTestExpectations):
     self.Skip('ContextLost_WebGLContextLostFromSelectElement',
               ['lion', 'debug'], bug=498149)
 
-    # Flaky on Mac 10.12 Intel Debug
-    self.Flaky('ContextLost_WebGLContextLostFromGPUProcessExit',
-        ['sierra', 'intel', 'debug'], bug=762745)
-
     # 'Browser must support tab control' raised on Android
     self.Skip('GpuCrash_GPUProcessCrashesExactlyOncePerVisitToAboutGpuCrash',
               ['android'], bug=609629)