Reland of gpu_test: enable Pixel_OffscreenCanvasUnaccelerated2DGPUCompositing

content/test/gpu/gpu_tests/pixel_expectations.py

Index: content/test/gpu/gpu_tests/pixel_expectations.py
diff --git a/content/test/gpu/gpu_tests/pixel_expectations.py b/content/test/gpu/gpu_tests/pixel_expectations.py
index 18f33a5be83715fbe083d77ce482013041d05ebd..5391ee6a6891d95372bbd09d9a6d2921ddb2174a 100644
--- a/content/test/gpu/gpu_tests/pixel_expectations.py
+++ b/content/test/gpu/gpu_tests/pixel_expectations.py
@@ -30,9 +30,8 @@ class PixelExpectations(GpuTestExpectations):
     # TODO(vmiura) check / generate reference images for Android devices
     self.Fail('Pixel_SolidColorBackground', ['mac', 'android'], bug=624256)
 
-    self.Fail('Pixel_OffscreenCanvasUnaccelerated2DGPUCompositing', bug=615325)
     self.Fail('Pixel_OffscreenCanvasUnaccelerated2DGPUCompositingWorker',
-              bug=615325)
+              ['mac', ('nvidia', 0xfe9)], bug=652931)
 
     # TODO(kbr): flakily timing out on this configuration.
     self.Flaky('*', ['linux', 'intel', 'debug'], bug=648369)