PRIVACY ISSUE
<video>/<audio> playback triggers a notification for the duration of playback.  These notifications are viewable in the notifications log for a while after the incognito tab (and chrome) are closed, potentially leaking privacy-sensitive info.
IMO incognito playbacks should prefer to preserve privacy (by not showing a notification) over the usability enhancement of having the persistent notification during playback.  (note that the Incongito notification will still show, and that's maybe also problematic, but seems like a different issue)

VERSION:
Chrome Version: 54.0.2840.85 stable
Operating System: Android NDE63V (and at least also on M, but probably all the way back to JB 4.3)

REPRODUCTION STEPS
- browse in incognito mode
- play a youtube video, at least long enough for the notification to show
- close all incognito tabs, side-swipe-kill chrome from Recents

Expect: no evidence of the video playback remains on device
Actual: Notification Log shows the following info until its flushed from the log's queue (by enough other notifications being shown later) or until device restart.

Johny Johny Yes Papa and Many More Videos | Popular Nursery Rhymes Collection by ChuChu TV - YouTube [Mon Nov 28 09:51:13 PST 2016]
Chrome
pkg: com.android.chrome
key: 0|com.android.chrome|2131558444|null|10056
icon: Icon(typ=RESOURCE pkg=com.android.chrome id=0x7f020053)
sound: none
vibrate: none
visibility: PRIVATE
priority: DEFAULT
intent: Intent(pkg=com.android.chrome (activity))
delete intent: Intent(pkg=com.android.chrome)
actions
  0 title: Play
    intent: Intent(pkg=com.android.chrome)
extras
  android.title: Johny Johny Yes Papa and Many More Videos | Popular Nursery Rhymes Collection by ChuChu TV - YouTube
  android.subText: https://m.youtube.com
  android.template: android.app.Notification$MediaStyle
  android.showChronometer: false
  android.text: 
  android.progress: 0
  android.progressMax: 0
  android.showWhen: false
  android.infoText: null
  android.originatingUserId: 0
  android.progressIndeterminate: false
  android.remoteInputHistory: null
  android.compactActions: [I@eb05996
parcel size: 1760 ashmem: 0