See https://build.chromium.org/p/chromium.gpu.fyi/builders/Linux%20Release%20%28ATI%29/builds/48325

It looks like the set of tests that make up this were skipped on all platforms until r398843.

Some failing test output:

[ RUN      ] WebglConformance.deqp_functional_gles3_uniformbuffers_single_struct_array
(INFO) 2016-06-15 11:48:14,772 cache_temperature.EnsurePageCacheTemperature:55  PageCacheTemperature: any
[24697:24697:0615/114815:INFO:CONSOLE(11)] "ubo.single_struct_array.per_block_buffer.std140_vertex: Invalid std140 layout", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "ubo.single_basic_type: Tests created", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "ubo.single_basic_array: Tests created", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "ubo.single_struct: Tests created", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "ubo.single_struct_array: Tests created", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "ubo.single_nested_struct: Tests created", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "ubo.single_nested_struct_array: Tests created", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "ubo.instance_array_basic_type: Tests created", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "ubo.multi_basic_types: Tests created", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "ubo.multi_nested_struct: Tests created", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "ubo.random: Tests created", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "Init testcase: ubo.single_struct_array.per_block_buffer.std140_vertex", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "Active glsUniformBlockCase.Uniform Blocks", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "0: [object Object]", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "Active Uniforms", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "0: [object Object]", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "1: [object Object]", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "2: [object Object]", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "3: [object Object]", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "4: [object Object]", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "5: [object Object]", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "6: [object Object]", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "7: [object Object]", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "8: [object Object]", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "9: [object Object]", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "10: [object Object]", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "Error: Layout mismatch in 'v':
 expected: type = vec4, size = 1, row major = false
 got: type = vec4, size = 1, row major = false", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "FAIL Invalid std140 layout", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "Image comparison failed, got 9216 non-white pixels.", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "ubo.single_struct_array.per_block_buffer.std140_vertex: Image compare failed", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "FAIL Image compare failed", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "Init testcase: ubo.single_struct_array.per_block_buffer.std140_fragment", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "", source:  (11)
[24697:24697:0615/114815:INFO:CONSOLE(11)] "Active glsUniformBlockCase.Uniform Blocks", source:  (11)
...