Separate paste code from DirectoryFragment.

Also untie DocumentClipper from activities. We'll have a single
DocumentClipper across the app from now on.

Bug: 28742120
Change-Id: Ib9e2537c3499ba2fa0a203ddad3ae71246d5b009
(cherry picked from commit 0cd92d35c533c16b301bd228cce8c68a289407a1)
6 files changed