UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.84 Safari/537.36

Example URL:
http://codepen.io/AmeliaBR/pen/8713c723f84e1e637389a948a6c4d657?editors=1000

Steps to reproduce the problem:
1. Embed an interactive SVG or HTML document in a web page using an <object> element.
2. Try to reach the interactive content with the keyboard.
3. Test whether adding tabindex=0 to the <object> provides a way to access the embedded document.
4. Try to reach the <object> or the interactive content with the keyboard.
5. Despair.

(Or just check out the linked CodePen test case.)

What is the expected behavior?
The embedded document's tab order should be embedded in the parent document's tab order, the same as happens with an <iframe>.

What went wrong?
In Chrome 51, focus skips over the <object> completely when tabbing through the document.

If you transfer focus to the embedded document another way (e.g., click on the link, then reverse the navigation with the backspace key), you can still successfully tab *out* of that document and back into the parent document's tabindex.

Does it occur on multiple sites: Yes

Is it a problem with a plugin? No 

Did this work before? N/A 

Does this work in other browsers? Yes 

Chrome version: 51.0.2704.84  Channel: stable
OS Version: 10.0
Flash Version: Shockwave Flash 21.0 r0

I'm not 100% sure that this is a regression, but I'd like to think so.  Embedding interactive SVG via <object> is pretty standard, and I hope I would have noticed previously if it was completely inaccessible to keyboard users.

Firefox and Edge both allow the links in the embedded document to be reached by tabbing.  However, there are other browser inconsistencies: in Firefox, the <object> and <iframe> elements are added as tab stops, without the tabindex attribute; in Edge, the root <svg> element in the embedded document is a tab stop (a legacy of SVG 1.2 keyboard focus rules).  

PS, Possibly relevant bug on <object> and tabindex: https://bugs.chromium.org/p/chromium/issues/detail?id=531231 
But that's with respect to Flash objects, and the poster specifically says it wasn't a problem with HTML embeds.