Version: 51.0.2691.0
OS: Android

Following the steps below, an extra entry appears in the nav stack for the online copy of an offline page.  If someone is going "back" through the nav stack the first time will load the online version, and going "back" the second time will load the offline version of the same page.

1. Start Chrome with offline pages enabled, and have at least one offline page available (www.google.com/finance for the sake of this bug)
2. Navigate to an online page (news.yahoo.com)
3. Go offline
4. Navigate to the offline page (www.google.com/finance)
5. Go Online
6. Navigate to a different online page (xkcd.com)
7. Click back
8. Click back again

What is the expected output?

In #7 the online version of the page from #4 should load, In #8 the page from #2 should load.

What do you see instead?

In #8 the offline version of the page from #4 appears, so the same page appears twice in the nav stack one for the online and offline versions.

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