Revert of [gpu_tests] Disable flaky pixel tests

content/test/gpu/gpu_tests/pixel_expectations.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from gpu_tests.gpu_test_expectations import GpuTestExpectations
 
 # See the GpuTestExpectations class for documentation.
 
 class PixelExpectations(GpuTestExpectations):
   def SetExpectations(self):
@@ skipping 26 matching lines @@
     self.Flaky('*', ['linux', 'intel', 'debug'], bug=648369)
 
     # Flaky for unknown reasons only on macOS. Not planning to investigate
     # further.
     self.Flaky('Pixel_ScissorTestWithPreserveDrawingBuffer', ['mac'],
                bug=660461)
 
     # TODO(kainino): remove this once golden images are generated
     self.Fail('Pixel_WebGLTransparentGreenTriangle_NoAlpha_ImplicitClear',
               bug=666259)
-
-    self.Fail('Pixel_CSSFilterEffects_NoOverlays', ['mac'], bug=672999)
-    self.Fail('Pixel_Canvas2DRedBox', ['mac'], bug=672999)
-    self.Fail('Pixel_CanvasDisplayLinearRGBAccelerated2D', ['mac'], bug=672999)
-    self.Fail('Pixel_CanvasDisplayLinearRGBUnaccelerated2D', ['mac'],
-              bug=672999)
-    self.Fail('Pixel_CanvasDisplayLinearRGBUnaccelerated2DGPUCompositing',
-              ['mac'], bug=672999)
-    self.Fail('Pixel_IOSurface2DCanvas', ['mac'], bug=672999)
-    self.Fail('Pixel_OffscreenCanvasTransferToImageBitmapWorker', ['mac'],
-              bug=672999)
-    self.Fail('Pixel_WebGLGreenTriangle_NoAA_NoAlpha', ['mac'], bug=672999)