The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4314fd9c8498473c5e53a529e11d2678bd1a1ea2

commit 4314fd9c8498473c5e53a529e11d2678bd1a1ea2
Author: Weiyong Yao <braveyao@chromium.org>
Date: Fri Aug 04 21:50:36 2017

Android screencapture: restore heads-up notification on O

Since Android O, all notifications must be assigned to a registed
notification channel. The importance property of the channel decides
how the notification can interrupt user.
Chrome will show heads-up notification for screen capture before Android
O. To keep this feature, a notification channel with IMPORTANCE_HIGH must
be created for it. And this channel will be created on first use.

Bug:  734266 
Change-Id: Ic8e7a5c62d1d911fcf6a27dfb62dcc120dd9f240
Reviewed-on: https://chromium-review.googlesource.com/585246
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Reviewed-by: Anita Woodruff <awdf@chromium.org>
Commit-Queue: Weiyong Yao <braveyao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#492134}
[modify] https://crrev.com/4314fd9c8498473c5e53a529e11d2678bd1a1ea2/chrome/android/java/src/org/chromium/chrome/browser/media/MediaCaptureNotificationService.java
[modify] https://crrev.com/4314fd9c8498473c5e53a529e11d2678bd1a1ea2/chrome/android/java/src/org/chromium/chrome/browser/notifications/channels/ChannelDefinitions.java
[modify] https://crrev.com/4314fd9c8498473c5e53a529e11d2678bd1a1ea2/chrome/android/java/strings/android_chrome_strings.grd