[gpu_tests] Disable flaky pixel tests

BUG=672999
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

TBR=kbr@chromium.org,zmo@chromium.org

Review-Url: https://codereview.chromium.org/2569013005
Cr-Commit-Position: refs/heads/master@{#438166}

content/test/gpu/gpu_tests/pixel_expectations.py

@@ -47,3 +47,15 @@ class PixelExpectations(GpuTestExpectations):
     # 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)