Revert of [gpu_tests] Disable flaky pixel tests

content/test/gpu/gpu_tests/pixel_expectations.py

Index: 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 4c40cf79b273a579c9af453befe82e9040e4762b..757260a1d3372c036989a7d38859ca100f25bbf8 100644
--- a/content/test/gpu/gpu_tests/pixel_expectations.py
+++ b/content/test/gpu/gpu_tests/pixel_expectations.py
@@ -44,15 +44,3 @@
     # 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)