Auto Picture-in-Picture should apply only in the scope of the web app

TBR=beaufort.francois@gmail.com

(cherry picked from commit 0a5d0c6838cb1468b26dc2ec93eb26e382106adb)

Bug: 922884
Change-Id: Iab91cfdf83a8022b38a073532f9052732bb44296
Reviewed-on: https://chromium-review.googlesource.com/c/1436357
Auto-Submit: François Beaufort <beaufort.francois@gmail.com>
Commit-Queue: François Beaufort <beaufort.francois@gmail.com>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#628072}
Reviewed-on: https://chromium-review.googlesource.com/c/1451818
Reviewed-by: François Beaufort <beaufort.francois@gmail.com>
Cr-Commit-Position: refs/branch-heads/3683@{#157}
Cr-Branched-From: e51029943e0a38dd794b73caaf6373d5496ae783-refs/heads/master@{#625896}
5 files changed