Findit identified the culprit r572804 with confidence 100.0% in the config "chromium.linux / Linux Tests"
based on the flakiness trend:

https://findit-for-me.appspot.com/waterfall/flake?key=ag9zfmZpbmRpdC1mb3ItbWVy0gELEhdNYXN0ZXJGbGFrZUFuYWx5c2lzUm9vdCKbAWNocm9taXVtLmxpbnV4L0xpbnV4IFRlc3RzLzcwOTIxL3Zpel9icm93c2VyX3Rlc3RzL1VHbGpkSFZ5WlVsdVVHbGpkSFZ5WlZkcGJtUnZkME52Ym5SeWIyeHNaWEpDY205M2MyVnlWR1Z6ZEM1VGRYSm1ZV05sU1dSRGFHRnVaMlZFYjJWelRtOTBUVzkyWlZkcGJtUnZkdz09DAsSE01hc3RlckZsYWtlQW5hbHlzaXMYAQw

If the culprit above is wrong, please file a bug using this link and hit submit:
https://bugs.chromium.org/p/chromium/issues/entry?status=Unconfirmed&labels=Pri-1,Test-Findit-Wrong&components=Tools%3ETest%3EFindit%3EFlakiness&summary=%5BFindit%5D%20Flake%20Analyzer%20-%20Wrong%20result%20for%20PictureInPictureWindowControllerBrowserTest.SurfaceIdChangeDoesNotMoveWindow&comment=Link%20to%20Analysis%3A%20https://findit-for-me.appspot.com/waterfall/flake?key=ag9zfmZpbmRpdC1mb3ItbWVy0gELEhdNYXN0ZXJGbGFrZUFuYWx5c2lzUm9vdCKbAWNocm9taXVtLmxpbnV4L0xpbnV4IFRlc3RzLzcwOTIxL3Zpel9icm93c2VyX3Rlc3RzL1VHbGpkSFZ5WlVsdVVHbGpkSFZ5WlZkcGJtUnZkME52Ym5SeWIyeHNaWEpDY205M2MyVnlWR1Z6ZEM1VGRYSm1ZV05sU1dSRGFHRnVaMlZFYjJWelRtOTBUVzkyWlZkcGJtUnZkdz09DAsSE01hc3RlckZsYWtlQW5hbHlzaXMYAQw

Automatically posted by the findit-for-me app (https://goo.gl/Ot9f7N).

Revert is out in https://chromium-review.googlesource.com/c/chromium/src/+/1132978.

Uploading a CL to disable the test: https://chromium-review.googlesource.com/c/chromium/src/+/1133306

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4e73dbe75e32793f9eee2fd0a6ec08a50792d0e8

commit 4e73dbe75e32793f9eee2fd0a6ec08a50792d0e8
Author: Mounir Lamouri <mlamouri@chromium.org>
Date: Wed Jul 11 15:49:16 2018

Picture-in-Picture: disabling flaky tests while origin is investigated.

Bug:  862505 
Change-Id: I1bcb2019be64dbb91081e1f8d607aca4cb0fbdc5
TBR: apacible@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/1133306
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574176}
[modify] https://crrev.com/4e73dbe75e32793f9eee2fd0a6ec08a50792d0e8/chrome/browser/picture_in_picture/picture_in_picture_window_controller_browsertest.cc

I'm going to re-enable this test on all platforms to see if it is still flaky.
See https://chromium-review.googlesource.com/c/chromium/src/+/1243083

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/644556f5c135a5aeb14107f7915475dc21ca0bd9

commit 644556f5c135a5aeb14107f7915475dc21ca0bd9
Author: François Beaufort <beaufort.francois@gmail.com>
Date: Tue Sep 25 15:54:36 2018

Re-enable flaky test SurfaceIdChangeDoesNotMoveWindow.

Now that SetAspectRatio is implemented everywhere, this CL re-enables a
PictureInPictureWindowControllerBrowserTest test which was found flaky
previously.

Bug:  862505 
Change-Id: I884a1b1ff3fe131c671c5e1a5e8142bb5e7d9a8a
Reviewed-on: https://chromium-review.googlesource.com/1243083
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: François Beaufort <beaufort.francois@gmail.com>
Cr-Commit-Position: refs/heads/master@{#593950}
[modify] https://crrev.com/644556f5c135a5aeb14107f7915475dc21ca0bd9/chrome/browser/picture_in_picture/picture_in_picture_window_controller_browsertest.cc

I'll monitor https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Linux%20Tests.

I didn't find any flakyness so I think we're good.