Mark flaky WebGL conformance test on Mac Retina

content/test/gpu/gpu_tests/webgl_conformance_expectations.py

Index: content/test/gpu/gpu_tests/webgl_conformance_expectations.py
diff --git a/content/test/gpu/gpu_tests/webgl_conformance_expectations.py b/content/test/gpu/gpu_tests/webgl_conformance_expectations.py
index 3a069ffe7a95fc14b7ddde251b5ebebf70c9d9dd..45776a4dd4cf0cc46c940e08b8995c6f14cff856 100644
--- a/content/test/gpu/gpu_tests/webgl_conformance_expectations.py
+++ b/content/test/gpu/gpu_tests/webgl_conformance_expectations.py
@@ -377,6 +377,9 @@ class WebGLConformanceExpectations(GpuTestExpectations):
         ['mac', ('nvidia', 0xfe9)], bug=635081)
     self.Fail('conformance/textures/misc/tex-input-validation.html',
         ['mac', ('nvidia', 0xfe9)], bug=635081)
+    self.Flaky('conformance/uniforms/' +
+        'no-over-optimization-on-uniform-array-12.html',
+        ['mac', ('nvidia', 0xfe9)], bug=684903)
 
     # Mac ASAN only
     self.Fail(