Chrome Version       : 53.0.2785.57
OS Version: 10.0
URLs (if applicable) : chrome://history
Other browsers tested: none

UserAgentString: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.57 Safari/537.36
  
What steps will reproduce the problem?
1. start with md-history disabled or default=disabled, e.g. 53.0.2785.57 usage
2. open history page (Ctrl-H or otherwise)
3. change md-history to enabled (on the about:flags page), relaunch
4a. history tab blocks as 'chrome://chrome/history Not-Reachable' (usually), 
4b. reloads OK, 
 but displays in old (Settings Menu) layout
5. dismiss history tab
6. open history tab: displays in new MD layout (kebab menu)

What is the expected result?
At #4b, when reloaded, history should display with MD layout


What happens instead of that?
history displayed with old (settings menu) layout


Additional information: Since this only effects the developer community, i.e. when switching md-history modes, and will eventually be overcome by history, I'm not sure if this is worthwhile investigating.  It bit me because I was looking for the new features and kept getting the old design.  So for the record..

The reverse sequence is OK: start with md-history enabled and a history tab open, switch to disabled, relaunch; 
the history page reverts back to the old style.

Re: #4a: History page not reachable.  Not-reachable may not occur sometimes, 
the page may load initially OK - still with the old layout.

I ran through this 6+ times before I saw the pattern.  
Definitely repeatable (for me..)
Ping me if you need more details.