- Redefine Scheduler interface to better describe what implementations
do. The previous version was too general, in that it allowed concrete
DownloadService implementations to pass different Requirements to
the base class and to the Scheduler. It's also difficult to see how
that version could ever support dynamic updates to Requirements, which
is probably a feature we'll need to add quite soon.
- Fix a (probably theoretical) problem where static fields in
DownloadService assumed only a single concrete implementation.
- Stop using PlatformScheduler pre-API-21 in demo app, because it will
fail.
- Define default Requirements that require network.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=194785751
c6bedc6a85