UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.95 Safari/537.36

Steps to reproduce the problem:
1. Define custom element
2. Create node with document.createElement using tag name with uppercase characters

What is the expected behavior?
document.createElement() should work regardless of using lowercase or uppercase letters (ex. "custom-element" or "CUSTOM-ELEMENT").

MDN for createElement says:

When called on an HTML document, createElement() converts tagName to lower case before creating the element.

What went wrong?
Created node has HTMLElement as prototype (which normally would be HTMLUnknownElement) neither lifecycle events was not triggered.

Did this work before? No 

Does this work in other browsers? N/A

Chrome version: 55.0.2883.95  Channel: n/a
OS Version: OS X 10.12.2
Flash Version: Shockwave Flash 24.0 r0
 

Deleted: test.js 392 bytes

test.js 392 bytes View Download