Mark a flaky WebGL test

conformance/extensions/oes-texture-float-with-video.html on Win Intel

TBR=kbr@chromium.org
BUG=825338

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;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I2b3116e48264c503b034d1230f24555a639858db
Reviewed-on: https://chromium-review.googlesource.com/978038
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545625}

content/test/gpu/gpu_tests/webgl_conformance_expectations.py

@@ -281,6 +281,8 @@ class WebGLConformanceExpectations(GpuTestExpectations):
         ['win7', 'nvidia', 'd3d9'], bug=690248)
 
     # Win / Intel
+    self.Flaky('conformance/extensions/oes-texture-float-with-video.html',
+        ['win', 'intel'], bug=825338)
     self.Fail('conformance/rendering/rendering-stencil-large-viewport.html',
         ['win', 'intel', 'd3d11'], bug=782317)