To support high-density displays, we generate or fetch media thumbnails at
three resolutions: standard 1x, 1.5x, and 2.0x density.
When going over InstantCommons, this currently requires us to make three
separate thumbnail lookups over the internet, which are done in serial and together
make for a large latency in end-user response.
If support for requesting multiple thumbnail sizes at once is added to the imageinfo API (bug 54035), we should be able to use that in ForeignAPIRepo (aka 'InstantCommons') to fetch the URLs for the three densities in one HTTP request. This would reduce the round-trip time for third-party users of InstantCommons.