Large photo storage.

This change adds support for storing large photos for contacts in the
file system.  Large photos passed to the provider will be downscaled
and re-encoded as JPEGs before being stored in the usual data BLOB
field (for the thumbnail) and in the photo store (for the display
photo).

See go/large-photo-design for details.

Change-Id: I26a69ac2ccba631962a3ac5c83edb3f45d7cfc7f
19 files changed