When the dynamic media source contains multiple empty timelines in a row and some
of them dynamically change to a non-empty timeline, the window and period indices
are not updated correctly because the index of the changed child source is wrong.

To fix this bug, the child index is added to the media period holder to have direct
access on the current child index to prevent ambiguity.

Furthermore, the uid is changed to be the hash code of the MediaSourceHolder not the
MediaSource itself to allow adding the same MediaSource twice without violating the
unique uid policy.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183973462

Simplifies the app and prevents inconsistent states between
both players and the media queue.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183831329

Also fixes a bug where deferred media periods were kept in the list for
an unprepared media source although the media period was already released.

Issue:#3498

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183800889

This enables caching manifest files for DASH, HLS and SmoothStreaming.

To disable caching a non cache DataSource should be provided for reading
manifest to the used MediaSource.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183794252

In startReadWrite*() methods a new CachedContent is created if the there
isn't one already for the given key. If the span is release without
writing any content, this fix removes the added CachedContent.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183666821

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183656655

Before this change, the ad playback state stored the number of played ads in
each ad group. There was no way to represent that an ad had failed to load (and
it wouldn't be possible just to increment the played ad count to signal a load
error because there might be an unplayed ad before the ad that failed to load).

Represent the state of each ad (unavailable, available, skipped, played, error)
in each ad group. In a later change the player will use this information to
update its loaded MediaPeriods in response to future ads failing to load.

Also make the AdPlaybackState immutable and remove copying/duplication of its
fields in the ad timeline and period.

Issue: #3584

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183655308

For our strings to be translated, we're required to provide
added context in the form of a description, and specify a
maximum length for the translated strings.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183651515

Issue:#3498

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183648419

1. When we try and load something via reflection and find the
   class, always throw rather than failing silently if we
   subsequently fail to instantiate an instance. This is
   indicative of a broken proguard setup, and failing silently
   makes it hard to spot.
2. Add library/core proguard configuration to ensure extension
   renderer constructors that we access via reflection are kept.
3. Add demos/main proguard configuration to ensure ImaAdsLoader
   constructor that we access via reflection is kept.
4. Added IMA proguard file to hopefully fix #3723, although I
   wasn't actually able to reproduce the issue.

Issue: #3723

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183648187

- Renderers becoming ready is asynchronous, so the change wasn't
well thought through :(.
- This will bring back the possibility of getting stuck in the
buffering-but-not-loading anything state. This will need to be
addressed in a future CL.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183646837

100ms is unrealistically short and, for example, causes the player to buffer
many periods ahead when looping.

Previously this was not feasible, because ExoPlayerTest as instrumentation test
actually needed to wait for the realtime playback duration.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183646772

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183643457

It's really spammy. Decided not to document tag as also
being nullable in case we ever use it for anything else
in the base action class.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183632944

Only filter HlsMasterPlaylists.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183394956

GitHub:#3498

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183392095

GitHub:#3498

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183391117

MediaPeriodInfoSequence has functionality for determining what MediaPeriod
should be loaded next. Move this into the queue as an initial step towards
moving logic concerning updating the queue of media periods out of
ExoPlayerImplInternal.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183391114

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183390851

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183389701

This removes some boiler-plate code for compostite sources and will also
simplify resuing media source in the future (because this class can keep track
of child listeners).

Issue:#3498

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183387123

GitHub:#3498

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183378776

This is only allowed for user-replaced manifest uris. If the manifest
itself forwards to another manifest, we keep the original manifest in
case the forwarding changes.

Also removed the initialManifest as it can be simplified by using the
sideloadedManifest indicator.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183376209

GitHub:#3498

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183373647

GitHub:#3498

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183369041

Issue:#3747

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183366339

GitHub:#3498

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183253017

When SsMediaSource loads Manifest, it dispatches loadCompleted event even when
the load is cancelled. This change makes sure SsMediaSource dispatch
loadCancelled event instead.

GitHub: #3754

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183241940

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183238240

Since AspectRatioFrameLayout supports zoom mode as another resize_mode,
PlayerView's resize mode xml attribute should include this as well.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183237663

Helper class to create notifications for downloads using DownloadManager.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183225948

- This gives LoadControl enough information in shouldContinueLoading
  to know whether returning false will result in a terminal non-playback
  state.
- DefaultLoadControl will always return true when returning false will
  result in a terminal non-playback state, unless the target buffer size
  is exceeded. This can help to avoid getting stuck in the case that a
  MediaPeriod is providing samples from an unexpected starting time.
- Make the terminal state actually terminal. Previously the player would
  end up in an indefinite buffering state. We now fail with an error.
- Also remove the opportunity for LoadControl implementations to livelock
  playback. No sane LoadControl should simultaneously tell the player that
  it doesn't want to load anything and that it doesn't want to start
  playback. So this change removes the opportunity and starts playback in
  EPII instead in this case.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183114797

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183102837

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183098172

Try to delay failure for as long as possible. That is, propagate
DRM session failures only after an encrypted buffer arrives or clear
sample playback without session is not allowed.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183076348

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183068548

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183065262

add support in mediacodecaudiorenderer for 24bit pcm to float