For the new documents work, we're only interested in the subset of
ContentProviders that actually implement DocumentsContract. Instead
of returning all providers, add <intent-filter> support to make it
easier to limit the set of returned ProviderInfo.
Define a well-known action for DocumentsProviders, and start using it
when querying for roots. Continue supporting the old <meta-data>
approach until all apps have been updated.
Bug: 8599233
Change-Id: I05f049bba21311f5421738002f99ee214447c909
85f5f81320