Remove pixel test suppressions

Submit this after all bots have generated new reference images for these
tests.

Bug: 899399
Change-Id: Ib3a48a5955796e9e3638b11a6176bb8e935ebfe1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1568387
Commit-Queue: Bo <boliu@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#651771}

content/test/gpu/gpu_tests/test_expectations/pixel_expectations.txt

@@ -171,15 +171,3 @@ crbug.com/929425 [ win nvidia ] Pixel_DirectComposition_ComplexOverlays [ RetryO
 
 # Mark all webview tests as RetryOnFailure due to Nexus 5x driver bug.
 crbug.com/950932 [ android-webview-instrumentation qualcomm-adreno-(tm)-418 ] * [ RetryOnFailure ]
-
-# Mark pixel tests as failure to generate new ref images with gpu raster for android webview.
-crbug.com/899399 Pixel_2DCanvasWebGL [ Failure ]
-crbug.com/899399 Pixel_BackgroundImage [ Failure ]
-crbug.com/899399 Pixel_Canvas2DRedBox [ Failure ]
-crbug.com/899399 Pixel_CanvasDisplayLinearRGBAccelerated2D [ Failure ]
-crbug.com/899399 Pixel_CanvasLowLatency2D [ Failure ]
-crbug.com/899399 Pixel_WebGLGreenTriangle_AA_Alpha [ Failure ]
-crbug.com/899399 Pixel_WebGLGreenTriangle_AA_NoAlpha [ Failure ]
-crbug.com/899399 Pixel_WebGLGreenTriangle_NoAA_Alpha [ Failure ]
-crbug.com/899399 Pixel_WebGLGreenTriangle_NoAA_NoAlpha [ Failure ]
-crbug.com/899399 Pixel_WebGLTransparentGreenTriangle_NoAlpha_ImplicitClear [ Failure ]