Disable failing GpuProcess_webgl_disabled_extension test

This is failing on the N9 FYI bot, see issue 895945.

TBR=kbr@chromium.org

Bug: 895945
Change-Id: Ib735cbfcc04e334cc9204acf8ccc2792239323c5
Reviewed-on: https://chromium-review.googlesource.com/c/1283952Reviewed-by: Eric Karl <ericrk@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600109}

content/test/gpu/gpu_tests/gpu_process_expectations.py

@@ -16,3 +16,5 @@ class GpuProcessExpectations(GpuTestExpectations):
     # Test needs fixing for Nexus 9
     self.Fail('GpuProcess_disabling_workarounds_works', ['android', 'nvidia'],
               bug=895020)
+    self.Fail('GpuProcess_webgl_disabled_extension', ['android', 'nvidia'],
+              bug=895945)