Re-enable Pixel_DirectComposition_Video_MP4

The baseline for the new version should be generated now.

BUG=704389
TBR=kbr@chromium.org
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_optional_gpu_tests_rel;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

Review-Url: https://codereview.chromium.org/2905413003
Cr-Commit-Position: refs/heads/master@{#475253}

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 a703f6c..c230f4f 100644
--- a/content/test/gpu/gpu_tests/pixel_expectations.py
+++ b/content/test/gpu/gpu_tests/pixel_expectations.py
@@ -55,9 +55,6 @@
     # TODO(zakerinasab): check / generate reference images.
     self.Fail('Pixel_Canvas2DUntagged', bug=713632)
 
-    # TODO(jbauman): Remove when new baseline exists.
-    self.Fail('Pixel_DirectComposition_Video_MP4', bug=704389)
-
     # Failures on Haswell GPUs on macOS after upgrade to 10.12.4.
     self.Fail('Pixel_OffscreenCanvas2DResizeOnWorker',
               ['mac', ('intel', 0x0a2e)], bug=718183)