AW docs: document Dev UI options menu

This documents the cool stuff hiding in Dev UI's options menu. This also
links to instructions for hooking up WebView to Chrome DevTools, in case
folks find this page looking for that.

Bug: 1058571
Test: tools/md_browser/md_browser.py
Test: Upload to gerrit > open file > click "gitiles"
Change-Id: I6ecd5ac4b8e102b36a5cbdd28c9ce60958057a99
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2144263
Commit-Queue: Richard Coles <torne@chromium.org>
Auto-Submit: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758203}

android_webview/docs/developer-ui.md

@@ -118,3 +118,32 @@ Exposing your feature this way has several benefits:
 ### See also
 
 - [Design doc](http://go/webview-dev-ui-flags-design) (Google-only)
+
+## More cool stuff
+
+### Switching WebView provider
+
+Since Android 7 (Nougat), Android supports installing [multiple WebView
+packages](prerelease.md) side by side and switching between them. After
+installing the WebView channel you want, launch WebView DevTools, open the
+three-dotted menu, and select "Change WebView Provider." This launches the
+system UI where you can select your new WebView channel.
+
+### Filing a bug report
+
+*** aside
+This was [added in M84](https://chromiumdash.appspot.com/commit/874adae46ba404dfec1660ef239899eef47d72bc).
+***
+
+You can file general bug reports for the WebView engineering team. Launch
+WebView DevTools, open the three-dotted menu, and select "Report WebView Bug."
+Similar to filing bug reports for crashes, this will open the system browser to
+[our bug
+tracker](https://bugs.chromium.org/p/chromium/issues/entry?template=Webview+Bugs&labels=Via-WebView-DevTools)
+(requires sign-in), where you can describe the issue.
+
+## Looking for Chrome DevTools?
+
+You can debug WebView even more with Chrome DevTools! For detailed instructions,
+check out [Remote Debugging
+WebViews](https://developers.google.com/web/tools/chrome-devtools/remote-debugging/webviews).