There are several similar entries in stackoverflow for this error (HTTP 400), but I haven't found anything relevant to mine; so if this is already answered... my apologies.
Chrome is my default browser, and I use many Google services everyday, like Gmail, Maps, Docs, etc.
However, time-to-time, when I am logged-in to Google, I notice some assets are not loading from Google websites (*.google.com).
For example; Google logo in upper-left corner at main www.google.com search results; or image tiles in Maps.
Those missing images (or assets in general images, JS, CSS) have references in the DevTools Console: Failed to load resource: the server responded with a status of 400
Once I clear storage in DevTools > Application, naturally I get logged out, but those missing assets start behaving normal and load as expected. I can log back in to Google services and use them without any issues, until next time it happens.
Since clearing storage (cookies and cache) fixes the issue, I don't think it's related with any of the installed add-ons (read AdBlock).
Has anyone experienced this issue, or better yet have a solution for this? Or should I continue blaming Google in general? :)
I was having a similar issue in Maps. I searched around on the intertubes and found a solution that worked for me: https://productforums.google.com/forum/#!topic/maps/zbT4TK4x2QI
Synopsis: delete all the cookies for "www.google.com" starting with gsScrollPos
In Chrome:
Hope that helps you!