Stats: graph timeframe does not update when viewing historical stats

[designsimply]

Steps to reproduce:

1. Go to https://wordpress.com/stats/month (or /days) and select a site if prompted.
2. Make sure the site select has more than a year (or more than 30 days) worth of stats.
3. Click the left arrow next to the main heading on the page until you navigate past the first bar on the left side of the graph.

Result: the graph doesn't update but the data on the page below does.

^{Seen at https://wordpress.com/stats/day/cute.wordpress.com?startDate=2016-12-26 using Chrome 55.0.2883.95 on Mac OS X 10.12}