WebGL: Mark glsl-mat4-to-mat3 flaky on Win/D3D9.

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 de105da2bafe57a66ea7609bcdfdf0813710097f..0680ef71e2e6ae9fdc0f432ad4b6da3de234774f 100644
--- a/content/test/gpu/gpu_tests/webgl_conformance_expectations.py
+++ b/content/test/gpu/gpu_tests/webgl_conformance_expectations.py
@@ -426,6 +426,8 @@ class WebGLConformanceExpectations(GpuTestExpectations):
     # The functions test have been persistently flaky on D3D9
     self.Flaky('conformance/glsl/functions/*',
         ['win', 'd3d9'], bug=415609)
+    self.Flaky('conformance/glsl/matrices/glsl-mat4-to-mat3.html',
+        ['win', 'd3d9'], bug=617148)
 
     # WIN / D3D9 / Intel failures
     self.Fail('conformance/ogles/GL/cos/cos_001_to_006.html',