I jumped the gun before: there's no ShapeDetection implementation in Linux, but
for the purposes of LayoutTests, we use JS mocks implementing the mojo interface,
so this should work:

out/gn/content_shell --run-layout-test --no-sandbox   third_party/WebKit/LayoutTests/shapedetection/detection-HTMLVideoElement.html

(important:  --run-layout-test modifier for content_shell).

OTOH there seems to be an issue with the comparison next to [1], in the
sense that WHITE is not exactly 0xFFFFFFFF, but 0xFFFFFEFF in Linux;
since this comparison doesn't make any sense (we are not interested 
in the actual colour), I'll remove it.

white.webm is a 10K webm video, so it should be playable by the bots, but
it might be slow indeed, so the indication in [2] is legitimate, but those
in [3] and [4] shouldn't, right?



[1] https://cs.chromium.org/chromium/src/third_party/WebKit/LayoutTests/shapedetection/detection-HTMLVideoElement.html?sq=package:chromium&dr&l=41
[2] https://cs.chromium.org/chromium/src/third_party/WebKit/LayoutTests/SlowTests?type=cs&q=shapedetection/detection-HTMLVideoElement.html&sq=package:chromium&l=440
[3] https://cs.chromium.org/chromium/src/third_party/WebKit/LayoutTests/MSANExpectations?type=cs&q=shapedetection/detection-HTMLVideoElement.html&sq=package:chromium&l=32
[4] https://cs.chromium.org/chromium/src/third_party/WebKit/LayoutTests/TestExpectations?type=cs&q=shapedetection/detection-HTMLVideoElement.html&sq=package:chromium&l=99

Ok, so if we keep only [2] and can remove [3] and [4], it's already a good improvement.

Note that, about [1], this is likely related to crbug.com/774567.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7eb5b5b3cd0e077b49124cec469eaf3d52778f5e

commit 7eb5b5b3cd0e077b49124cec469eaf3d52778f5e
Author: Miguel Casas-Sanchez <mcasas@chromium.org>
Date: Tue Oct 17 18:52:23 2017

ShapeDetection: remove pixel-value comparison from detection-HTMLVideoElement LayoutTest

This CL removes the pixel-value comparison from detection-HTMLVideoElement.html
LayoutTest because it has platform quirks, e.g. in Linux the white colour is
read back as 0xFFFFFEFF, breaking the comparison.

Bug: 775127
Change-Id: I563f208bf858da80813631e0f2a66181bf94375b
Reviewed-on: https://chromium-review.googlesource.com/721886
Reviewed-by: Emircan Uysaler <emircan@chromium.org>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#509463}
[modify] https://crrev.com/7eb5b5b3cd0e077b49124cec469eaf3d52778f5e/third_party/WebKit/LayoutTests/shapedetection/detection-HTMLVideoElement.html