Tested the issue in Android and able to reproduce the issue. 

Steps Followed:
1. Launch Chrome.
2. Navigate to any URL - https://assets-staging.nfc.9yrds.net/upload/video/c727a127-2b61-4d34-b59e-f6ea423bd458/original
3. Start playing the video.
4. Switch to full screen mode.
5. Observed that aspect ratio of the video gets disturbed and it is not same as in the normal mode.

Chrome versions tested:
66.0.3359.158(Stable), 69.0.3444.0(Canary)

OS:
Android 8.1.0

Android Devices:
Pixel 2 XL

Using the per-revision bisect providing the bisect results,
Good Build - 62.0.3181.0 (493197)
Bad Build - 62.0.3182.0 (493619)

You are looking for a change made after 493382(GOOD), but before 493383(BAD).

CHANGELOG URL:
The script might not always return single CL as suspect as some perf builds might get missing due to failure.
https://chromium.googlesource.com/chromium/src/+/a2d345d5b1fdd4c871344c58d928774e5bfa4be1

@liberato:  Could you please look into the issue, pardon me if it has nothing to do with your changes and if possible please assign it to owner concerned.

Please navigate to below link for log's and video--
go/chrome-androidlogs/847338

Note: This issue is not observed in FireFox mobile version.

Thanks!

Since this is a recent regression and has a clear suspect. Can we have a fix during M69 time frame?

not sure that this is rbs -- that change just flips a switch to switch how we handle overlay video on android.  i'm not even sure the old path works anymore -- i've been dismantling it, or at least not updating it.

it does sound suspiciously like 847338 -- i'll see what's different.

i see what's going on.  part of the switch to the new overlay system mentioned in c#3 gave more control to the decoders to choose overlays.  i thought that was in 64, but maybe part of it was in 62.

anyway, the decoders don't realize that rotated video is unsupported.  that used to be managed elsewhere.

fix out for review: https://chromium-review.googlesource.com/c/chromium/src/+/1085691

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6827e41808073f132794bcff63a8efcc99e68691

commit 6827e41808073f132794bcff63a8efcc99e68691
Author: liberato@chromium.org <liberato@chromium.org>
Date: Wed Jun 06 01:54:06 2018

Turn off overlays for rotated video.

Previously, WMPI checked the video rotation and didn't enable
overlays if it was nonzero.  During the switch to AndroidOverlay,
this is now the decoder's job.  This CL tells MCVD to do that.

Bug:  847338 
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: Ic76c91db1dd37e7e4160e5e7a17e2951b000884b
Reviewed-on: https://chromium-review.googlesource.com/1085691
Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
Commit-Queue: Frank Liberato <liberato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564766}
[modify] https://crrev.com/6827e41808073f132794bcff63a8efcc99e68691/media/gpu/android/android_video_surface_chooser.h
[modify] https://crrev.com/6827e41808073f132794bcff63a8efcc99e68691/media/gpu/android/android_video_surface_chooser_impl.cc
[modify] https://crrev.com/6827e41808073f132794bcff63a8efcc99e68691/media/gpu/android/android_video_surface_chooser_impl_unittest.cc
[modify] https://crrev.com/6827e41808073f132794bcff63a8efcc99e68691/media/gpu/android/media_codec_video_decoder.cc
[modify] https://crrev.com/6827e41808073f132794bcff63a8efcc99e68691/media/gpu/android/surface_chooser_helper.cc
[modify] https://crrev.com/6827e41808073f132794bcff63a8efcc99e68691/media/gpu/android/surface_chooser_helper.h
[modify] https://crrev.com/6827e41808073f132794bcff63a8efcc99e68691/media/gpu/android/surface_chooser_helper_unittest.cc

given how long this was broken, not sure if it's worth merging to 68.  however, it's fairly low risk.

Your change meets the bar and is auto-approved for M68. Please go ahead and merge the CL to branch 3440 manually. Please contact milestone owner if you have questions.
Owners: cmasso@(Android), kariahda@(iOS), bhthompson@(ChromeOS), abdulsyed@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/74a8671d0404d8ce882f19b26325bf99880e3584

commit 74a8671d0404d8ce882f19b26325bf99880e3584
Author: liberato@chromium.org <liberato@chromium.org>
Date: Thu Jun 07 17:47:01 2018

Turn off overlays for rotated video.

Previously, WMPI checked the video rotation and didn't enable
overlays if it was nonzero.  During the switch to AndroidOverlay,
this is now the decoder's job.  This CL tells MCVD to do that.

Bug:  847338 
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: Ic76c91db1dd37e7e4160e5e7a17e2951b000884b
Reviewed-on: https://chromium-review.googlesource.com/1085691
Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
Commit-Queue: Frank Liberato <liberato@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#564766}(cherry picked from commit 6827e41808073f132794bcff63a8efcc99e68691)
Reviewed-on: https://chromium-review.googlesource.com/1091171
Reviewed-by: Frank Liberato <liberato@chromium.org>
Cr-Commit-Position: refs/branch-heads/3440@{#238}
Cr-Branched-From: 010ddcfda246975d194964ccf20038ebbdec6084-refs/heads/master@{#561733}
[modify] https://crrev.com/74a8671d0404d8ce882f19b26325bf99880e3584/media/gpu/android/android_video_surface_chooser.h
[modify] https://crrev.com/74a8671d0404d8ce882f19b26325bf99880e3584/media/gpu/android/android_video_surface_chooser_impl.cc
[modify] https://crrev.com/74a8671d0404d8ce882f19b26325bf99880e3584/media/gpu/android/android_video_surface_chooser_impl_unittest.cc
[modify] https://crrev.com/74a8671d0404d8ce882f19b26325bf99880e3584/media/gpu/android/media_codec_video_decoder.cc
[modify] https://crrev.com/74a8671d0404d8ce882f19b26325bf99880e3584/media/gpu/android/surface_chooser_helper.cc
[modify] https://crrev.com/74a8671d0404d8ce882f19b26325bf99880e3584/media/gpu/android/surface_chooser_helper.h
[modify] https://crrev.com/74a8671d0404d8ce882f19b26325bf99880e3584/media/gpu/android/surface_chooser_helper_unittest.cc

Did not see an issue with the video as attached on Acer Predator (X86_64) and Chrome 68.0.3440.23