Revert "Revert "Add device document to MtpDatabase.""

I suspected that the commit was conflicted with ag/833494, but actually it wasn't. Let me reland this CL again.

This reverts commit b63e8c6ccc1425d56f8b9c801f4bddf906d694e5.

Change-Id: I4e734422ce10ef93ee7c4ef3b8b72a81beaa769b
9 files changed