Supress failures in the new framebuffer filter srgb WebGL 2 test on Linux.

TBR=zmo@chromium.org
CQ_INCLUDE_TRYBOTS=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;master.tryserver.chromium.android:android_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2346753003
Cr-Commit-Position: refs/heads/master@{#418885}

content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

@@ -462,6 +462,8 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
         ['linux', 'amd', 'intel'], bug=483282)
     self.Fail('deqp/data/gles3/shaders/linkage.html',
         ['linux', 'amd', 'intel'], bug=483282)
+    self.Fail('conformance2/rendering/blitframebuffer-filter-srgb.html',
+        ['linux', 'amd', 'intel'], bug=634525)
 
     # Linux with ANGLE only
     self.Fail('conformance2/textures/misc/tex-unpack-params.html',