UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36

Steps to reproduce the problem:
1. In a blank contenteditable, enter a blank line followed by a line with some text (ex "123456789")
2. Select All and copy
3. Paste twice and review HTML generated.

What is the expected behavior?
Before you copy/paste. the HTML will look like this:

<div><br></div><div>123456789</div>

After copying pasting twice on windows you would expect to get this:

<div><br></div><div>123456789</div><div><br></div><div>123456789</div>

What went wrong?
On Windows you end up with this: 

<br><div>123456789<br></div><div><br></div>123456789

Notice the first BR has been unwrapped as well as the last text element.

On Mac you end up with this: 

<br class="Apple-interchange-newline">123456789<br class="Apple-interchange-newline">123456789<br>

Notice the DIVs have been stripped altogether.

HTML generated from paste operation should be predictable.

Sample file used is attached.

Did this work before? N/A 

Chrome version: 53.0.2785.143  Channel: stable
OS Version: OS X 10.11.5
Flash Version: Shockwave Flash 23.0 r0

As noted this happens on Mac and Windows. I've tried it Canary on Windows and Mac the the results are the same in 53 and 56.0.2886.0 on each platform
 

Deleted: index0.html 200 bytes

index0.html 200 bytes View Download