Mark conformance/extensions/angle-instanced-arrays.html failing.

Mark this test failing on Linux/NVIDIA because it's too flaky to retry.

BUG=544989
TBR=zmo@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/1471963003

Cr-Commit-Position: refs/heads/master@{#361244}

content/test/gpu/gpu_tests/webgl_conformance_expectations.py

@@ -221,8 +221,8 @@ class WebGLConformanceExpectations(GpuTestExpectations):
     # NVIDIA
     self.Fail('conformance/textures/misc/default-texture.html',
         ['linux', ('nvidia', 0x104a)], bug=422152)
-    self.Flaky('conformance/extensions/angle-instanced-arrays.html',
-               ['linux', 'nvidia'], bug=544989)
+    self.Fail('conformance/extensions/angle-instanced-arrays.html',
+              ['linux', 'nvidia'], bug=544989) # Too flaky to retry
     self.Flaky('conformance/extensions/oes-element-index-uint.html',
                ['linux', 'nvidia'], bug=524144)
     # AMD Radeon 5450