UI hangs when typing in request body

Q&A (please complete the following information)

• OS: [Windows 10 Education]
• Browser: [Chrome]
• Version: [71.0.3578.98 (Official Build) (64-bit)]
• Method of installation: [NSwag, Swagger editor]
• Swagger-UI version: [3.19.0-3.20.3]
• Swagger/OpenAPI version: [OpenAPI 3.0.0]

Content & configuration

Example Swagger/OpenAPI definition:
https://pastebin.com/raw/Zh5ZGN17
Note: This spec is obfuscated

Swagger-UI configuration options:
Swagger editor default settings

Describe the bug you're encountering

Every key press in the request body takes about ~800 ms to process. The ui hangs and freezes while typing and opening operations also takes a very long time.

To reproduce...

Steps to reproduce the behavior:

1. Go to any post operation
2. Click on try it out
3. Type in the request body field
4. The UI will hang for a while for each keystroke, the more keystrokes the longer

Expected behavior

The UI does not hang or only for a very short time when entering words in the request body text field.

Additional information

Callstack of a single key press event:

Reproduce the slowdown in Swagger UI 3.19.0–3.20.3 using the provided OpenAPI definition, a POST operation, and the request body field in Chrome. Start with the reported keypress call stack and browser profiling; done means typing and opening operations no longer incur the reported per-keystroke hangs.