Mark a WebGL test Flaky

conformance/extensions/oes-texture-half-float-with-video.html
on Win7 Debug NVIDIA D3D11 passthrough

BUG=751849
TBR=kbr@chromium.org

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: Ieb623f457fca5937b8c82943f60ee87f7353febb
Reviewed-on: https://chromium-review.googlesource.com/599451
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491636}

content/test/gpu/gpu_tests/webgl_conformance_expectations.py

@@ -196,6 +196,8 @@ class WebGLConformanceExpectations(GpuTestExpectations):
         ['win', 'amd', 'passthrough', 'd3d11'], bug=685232)
 
     # Win / NVIDIA / Passthrough command decoder / D3D11
+    self.Flaky('conformance/extensions/oes-texture-half-float-with-video.html',
+        ['win7', 'nvidia', 'passthrough', 'd3d11', 'debug'], bug=751849)
     self.Flaky('conformance/programs/program-test.html',
         ['win', 'nvidia', 'passthrough', 'd3d11'], bug=737016)