Taking this.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5921862bd10d297e759a5ebf28bb90aba5b87650

commit 5921862bd10d297e759a5ebf28bb90aba5b87650
Author: zqzhang <zqzhang@chromium.org>
Date: Wed Dec 07 22:18:55 2016

[MediaNotification] Unset previous custom large icon correctly

In this CL, the custom large icon in media notification is unset (falling back
to favicon or default icon) in the following conditions:

* The newly-set MediaMetadata has no valid MediaImage,
* Downloading MediaImage failed.

Test page:
http://xxyzzzq.github.io/sandbox/media-session/full-test-artwork.html

BUG= 672015 
Test=Manual

Review-Url: https://codereview.chromium.org/2554013004
Cr-Commit-Position: refs/heads/master@{#437084}

[modify] https://crrev.com/5921862bd10d297e759a5ebf28bb90aba5b87650/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaImageCallback.java
[modify] https://crrev.com/5921862bd10d297e759a5ebf28bb90aba5b87650/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaImageManager.java
[modify] https://crrev.com/5921862bd10d297e759a5ebf28bb90aba5b87650/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaNotificationManager.java

I'm still able to reproduce this issue at https://beaufortfrancois.github.io/sandbox/media-session/playground.html in latest Chrome Canary for Android (57.0.2946.0) ;(

Sorry for the incomplete fix, I'll work on it :)

I see it's actually fixed, but the notification image only refreshes when the new image download finishes/fails. This is WAI to avoid the image flickering too much.

If the image is too large, it may take a while to download it, thus the previous image is still in use.

BTW I found there are cases where the image is successfully downloaded but not shown in the notification ( https://crbug.com/673360 ), will send a fix shortly.