Remove failed entries in gpu pixel expectations

The reference images generated for Accelerated2D and
Unaccelerated2D cases look correct.

TBR=zmo@chromium.org
BUG=655311
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://chromiumcodereview.appspot.com/2423413002
Cr-Commit-Position: refs/heads/master@{#426503}

content/test/gpu/gpu_tests/pixel_expectations.py

@@ -44,11 +44,3 @@ class PixelExpectations(GpuTestExpectations):
 
     # TODO(kbr): flakily timing out on this configuration.
     self.Flaky('*', ['linux', 'intel', 'debug'], bug=648369)
-
-    # TODO(xlai): check / generate reference images.
-    self.Fail('Pixel_OffscreenCanvasAccelerated2D', bug=655311)
-    self.Fail('Pixel_OffscreenCanvasAccelerated2DWorker', bug=655311)
-    self.Fail('Pixel_OffscreenCanvasUnaccelerated2D', bug=655311)
-    self.Fail('Pixel_OffscreenCanvasUnaccelerated2DWorker', bug=655311)
-    self.Fail('Pixel_OffscreenCanvasUnaccelerated2DGPUCompositing', bug=655311)
-    self.Fail('Pixel_OffscreenCanvasUnaccelerated2DGPUCompositingWorker', bug=655311)