Remove failing expectation on CSS3DBlueBox.

This pixel test is now passing on the bots, after a hardware change
to use the same GPU on all systems.

BUG=416719

Review URL: https://codereview.chromium.org/595323002

Cr-Commit-Position: refs/heads/master@{#296532}

content/test/gpu/gpu_tests/pixel_expectations.py

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