Mark the CSS3DBlueBox pixel test as failing.

There seems to be a problem with this test, as it seems to change
often after being rebaselined recently.

BUG=416719

Review URL: https://codereview.chromium.org/587753004

Cr-Commit-Position: refs/heads/master@{#296124}

content/test/gpu/gpu_tests/pixel_expectations.py

@@ -24,4 +24,6 @@ class PixelExpectations(test_expectations.TestExpectations):
     # self.Fail('Pixel.Canvas2DRedBox',
     #     ['mac', 'amd', ('nvidia', 0x1234)], bug=123)
 
+    self.Fail('Pixel.CSS3DBlueBox',bug=416719)
+
     pass