Device and version:
Pixel XL on OPP3.170518.006.

Apps that support Notification Channels get an "importance" setting with low/medium/high/urgent settings. Apps that don't support Notification Channels do not get an "importance" setting. This is a huge problem as it leaves users with no notification controls for 90% of apps, and a regression over Android N's "Power notification controls," which controlled notification importance for all apps.

* What are the steps to reproduce the problem? (Please provide the minimal reproducible test case.)
1. Navigate to Settings -> Apps & notifications -> App Info -> Phone (or anything with Notification Channels)
2. You can open "App Notifications," pick a notification category, and change the importance. This is great.
3. Now try an app that doesn't support notification channels, like Hangouts.
4. You can open "App Notifications," but with no channels, there is no way to access the importance settings.

* Issue Category: Framework (platform)

* What was the expected result?
The system needs to provide notification importance controls for all apps, regardless of whether or not they support notification channels. Many of the controls on the channel page are moved to the first page for apps with no channel controls (like "allow badge," "On the lock screen" and "Do not disturb override.") Please move the "importance" controls too.

* What was the actual result?
No notification channels = No notification controls.

* Optional: Link to any screenshot(s) that demonstrate the issue. (Attached. Public sharing is fine.)

https://drive.google.com/file/d/0BxI1YpjkbX0OT1Qwc3JxNFd0b2c/view?usp=drive_web (2017-06-22-18.27.jpg)