SDK / exoplayer

- I don't think the length is useful in hashCode; if the length
  is different then Arrays.hashCode should account for that.
- "this." just for consistency across these classes.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=116641142

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=116638211

This change replaces TrackGroup[] with TrackGroupArray. This is
to allow equality based hashCode and equals implementations.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=115563146

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=115561885

This change allows a TrackRenderer to distinguish between the
"I don't support this type at all" case and the "I am a general
purpose renderer of this type, but cannot support the specific
subtype" case.

Bug=26622675
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=115454950

The TrackSelector API will look like:

TrackSelection[] selectTrack(
    TrackRenderer[] renderers, TrackGroup[] trackGroups);

In this CL:

- SampleSources return TrackGroup[], so that the result can be easily
  passed to the selector.
- TrackStream gets its own file to sit alongside other Track* classes.
- A TrackSelection object is introduced to encapsulate group and track
  indices.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=115251331

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=114963314

- Add a top level failure type (source/renderer/unexpected),
  and convenience methods for retrieving the underlying cause
  without needing to cast.
- Also add renderer index in the case of renderer failures.
- setIndex/getIndex is a little . . . unclean, but alternatives
  involve either having the top line of the stack trace be a
  non-interesting line, or loads of try/catch blocks in
  ExoPlayerImplInternal.

Issue: #777
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=114763073

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=114743795

- Format can represent both container and sample formats.
  If a container contains a single track (as is true in
  DASH and SmoothStreaming) then the container Format can
  also contain sufficient information about the samples
  to allow for track selection. This avoids the Format to
  MediaFormat conversions that we were previously doing in
  ChunkSource implementations.

- One important result of this change is that adaptive
  format evaluation and static format selection now use the
  same format objects, which is a whole lot less confusing
  for someone who wants to implement both initial selection
  and subsequent adaptation logic. It's not in the V2 doc,
  but it may well make sense if the TrackSelector not only
  selects the tracks to enable for an adaptive playback, but
  also injects a FormatEvaluator when enabling them that will
  control the subsequent adaptive selections. That would make
  it so that all format selection logic originates from the
  same place.

- As part of this change, the adaptiveX variables are removed
  from the format object; they don't really correspond to a
  single format. This also saves on having to inject the max
  video dimensions through a bunch of classes.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=114546777

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=114545827

Duration was originally included in MediaFormat to match the
framework class, but it actually doesn't make much sense. In
many containers there's no such thing as per-stream duration,
and in any case we don't really care. Setting the duration on
each format required excessive piping.

This change moves duration into SeekMap instead, which seems
to make a lot more sense because it's at the container level,
and because being able to seek is generally couplied with
knowing how long the stream is.

This change is also a step toward merging Format and MediaFormat
into a single class (because Format doesn't have a duration),
which is coming soon.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=114428500

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=114427767

[Step 4 - Partial, of []

- The capabilities checks previously performed in VideoFormatSelectorUtil
  are now performed in MediaCodecVideoTrackRenderer. This means they'll be
  useful for non-chunk use cases (e.g. when using ExtractorSampleSource).
- Added capabilities checks for audio in MediaCodecAudioTrackRenderer. We
  didn't check audio capabilities previously.
- Added functionality to allow a TrackRenderer to indicate the extent of
  its adaptive support.

The idea here is that a TrackSelector (to be introduced) will have access to:

(a) TrackGroups from the SampleSource that indicate whether they support
adaptive playbacks and the formats of each individual track.
(b) TrackRenderers that indicate whether they support adaptive playbacks as
well as how capable they are of rendering formats of individual tracks.

This is everything that a TrackSelector needs from the player components in
order to decide how to wire things up. Note that a TrackSelector may opt to
treat FORMAT_EXCEEDS_CAPABILITIES as FORMAT_HANDLED at its own risk, if it
thinks that it (or the user) knows better. This is a request that we've seen
from third parties for better handling cases where capabilities aren't
accurately reported by the underlying platform.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=114427428

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=113868179

Delete SingleSampleChunkSource. I don't think it's really
useful for anything, now we have SingleSampleSource.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=113259289

This change removes the need for SourceBuilders to load their
manifests before building their sources. This is done by pushing
initial manifest loads into the ChunkSource classes. This simplifies
the SourceBuilders a lot, and also DemoPlayer.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=113259259

Notes:
1. The logic in ExoPlayerImplInternal is very temporary, until we
   have proper TrackSelector implementations. Ignore the fact that
   it's crazy and has loads of nesting.
2. This change removes all capabilities checking. TrackRenderer
   implementations will be updated to perform these checks in a
   subsequent CL.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=113151233

Move binding of tracks<->renderers to ExoPlayerImplInternal.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=113046018

GitHub note - Apologies for the cryptic change descriptions,
they relate to a design doc that's not externally visible.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=113043764

Fixes: #1176
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=112781092

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Created by MOE: https://github.com/google/moe
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MOE_MIGRATED_REVID=112774678

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=112736771

When a seek is performed, renderers currently perform the
actions that they need to take in two places: Some changes
are performed in seekTo implementations. Other changes are
performed when discontinuities are read from the source.

In HLS we need to perform what is effectively a seek
originating in the source. To support this, this CL allows
discontinuities read from the source to modify the playback
position. All actions that renderers perform as a result
of a seek are moved to be performed when a discontinuity is
received.

Best way to understand CL:
- Look at SampleSource interface change and then at the
  concrete implementations, to make sure they've been
  changed properly.
- Look at SampleSourceTrackRenderer change.
- Look at concrete renderers. The general pattern is that
  code previously performed in seekTo and READ_DISCONTINUITY
  is merged into onDiscontinuity().

Note: This will be further untangled in V2.

Issue #676
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=112720746

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=112699916

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=112699244

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=112693523

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=112691130

Based on AOSP's MP3Extractor.cpp and ID3.cpp.

Issue: #497
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=112685664

As part of this change, Extractor.sniff may read/skip (not just peek) if it
returns true. This allows Extractors to avoid parsing the input a second time in
read.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=112683272

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=112676296

Also fix a couple of style nits.