Note that the tab does NOT crash when we play video first before entering Picture-in-Picture.

Yes, the optimisation avoids creating the surface layer and getting frames until playback starts. Thanks for the clarification Francois.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/37e8ae8e13a72afb0b2f1a968efd161ef4b4b15b

commit 37e8ae8e13a72afb0b2f1a968efd161ef4b4b15b
Author: Mounir Lamouri <mlamouri@chromium.org>
Date: Thu May 31 02:38:46 2018

Picture-in-Picture: start pipeline to get surface id when needed.

In some cases, the pipeline will not be ready when trying to enter
Picture-in-Picture. It will happen if the video has preloaded its
metadata and has a poster. In this case, the Picture-in-Picture request
will be delayed until the pipeline has started and there is a surface.

Bug:  847671 
Change-Id: I56b0560db37ac2e6466abbd3f089973777c49f0f
Reviewed-on: https://chromium-review.googlesource.com/1077453
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Reviewed-by: apacible <apacible@chromium.org>
Commit-Queue: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563131}
[modify] https://crrev.com/37e8ae8e13a72afb0b2f1a968efd161ef4b4b15b/chrome/browser/picture_in_picture/picture_in_picture_window_controller_browsertest.cc
[add] https://crrev.com/37e8ae8e13a72afb0b2f1a968efd161ef4b4b15b/chrome/test/data/media/picture-in-picture/player_metadata_poster.html
[modify] https://crrev.com/37e8ae8e13a72afb0b2f1a968efd161ef4b4b15b/media/blink/webmediaplayer_impl.cc
[modify] https://crrev.com/37e8ae8e13a72afb0b2f1a968efd161ef4b4b15b/media/blink/webmediaplayer_impl.h

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

I'm not going to merge this given that we are not doing the OT M68.