This patch reworks SegmentIndexes so that any SegmentReference they
contain is guaranteed to be available. This makes SegmentIndexes work
consistently between static content and live content (specifically
content specified using SegmentTemplate with @duration).
* Rework StreamInfo to use a ISegmentIndexSource and a ISegmentInitSource,
which construct a SegmentIndex and an intiailization segment
respectively.
* Make ManifestInfo destructible and various async operations in
StreamVideoSource safer.
* Introduce LiveSegmentIndex, which manages SegmentReference eviction.
* Introduce DynamicLiveSegmentIndex, which manages SegmentReference
eviction and generation.
* Implement improved segment availability logic for segment eviction.
* Move SegmentIndex construction from MpdProcessor to several
ISegmentIndexSource implementations.
* Use a SegmentIndex to represent subtitles to simplify Stream creation
in StreamVideoSource.
* Move manifest update code from StreamVideoSource to ManifestUpdater.
* Move PeriodInfo.duration determination in MpdProcessor to StreamVideoSource.
* Since "forced" manifest updates are no longer required for content
specified using SegmentTemplate with @duration, simplify manifest update
code in DashVideoSource.
* Make Stream continue to update even if it runs out of
SegmentReferences, this simplifies previous resync logic and makes
DynamicLiveSegmentIndex work seamlessly.
* Refactor SegmentIndex and initialization fetch code in ContentDatabase.
* Download all SegmentIndexes in the background after the initial streams
have started.
Follow up work is required to remove seek range logic from
DashVideoSource.
Change-Id: I4a908195aba632a911a6e55213fc41d41428162b
Timothy Drews