Mark Pixel_WorkerRAF_OOPD tests as flaky

TBR=zmo

Bug: 840394
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: I61e8896bfff86145b124b9d4b24a59e5f31c756a
Reviewed-on: https://chromium-review.googlesource.com/1060014
Commit-Queue: Fernando Serboncini <fserb@chromium.org>
Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558842}

content/test/gpu/gpu_tests/pixel_expectations.py

@@ -94,8 +94,9 @@ class PixelExpectations(GpuTestExpectations):
     self.Fail('Pixel_CSS3DBlueBox_NoGpuProcess',
               ['linux', 'mac', 'win'], bug=744658)
 
-    # TODO(rjkroege): temporarily suppress this test.
+    # TODO(fserb): temporarily suppress this test.
     self.Flaky('Pixel_OffscreenCanvas2DResizeOnWorker', ['mac'], bug=840394)
+    self.Flaky('Pixel_WorkerRAF_OOPD', ['android', 'nvidia'], bug=840394)
 
     # TODO(kbr): temporary suppression for new test.
     self.Flaky('Pixel_WebGLSadCanvas', ['mac'], bug=575305)