MSE: Use TimeDelta for PTS in SourceBufferStream

With recent removal of LegacyByDts buffering logic, this change does
the last of the major cleanup to SourceBufferStream such that it now
uses base::TimeDelta for presentation time, removes the now-unnecessary
wrappers of SourceBufferRange that converted time type from/to
DecodeTimestamp, and updates the callers and tests of
SourceBufferStream's API.

Also adds a TODO around tangential compliance work remaining to fix
https://crbug.com/623729.

BUG=771349,623729

Change-Id: Ib87004719319ca34e917d54b1004ed111eab609c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1597544Reviewed-by: Dan Sanders <sandersd@chromium.org>
Commit-Queue: Matthew Wolenetz <wolenetz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658857}

media/filters/chunk_demuxer.cc

@@ -166,16 +166,13 @@ bool ChunkDemuxerStream::EvictCodedFrames(base::TimeDelta media_time,
   if (!is_enabled_)
     stream_->Seek(media_time);
 
-  // Note: The direct conversion from PTS to DTS is safe here, since we don't
-  // need to know currentTime precisely for GC. GC only needs to know which GOP
-  // currentTime points to.
-  DecodeTimestamp media_time_dts =
-      DecodeTimestamp::FromPresentationTime(media_time);
-  return stream_->GarbageCollectIfNeeded(media_time_dts, newDataSize);
+  // |media_time| is allowed to be a little imprecise here. GC only needs to
+  // know which GOP currentTime points to.
+  return stream_->GarbageCollectIfNeeded(media_time, newDataSize);
 }
 
 void ChunkDemuxerStream::OnMemoryPressure(
-    DecodeTimestamp media_time,
+    base::TimeDelta media_time,
     base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level,
     bool force_instant_gc) {
   base::AutoLock auto_lock(lock_);
@@ -240,7 +237,7 @@ void ChunkDemuxerStream::OnStartOfCodedFrameGroup(DecodeTimestamp start_dts,
     group_start_observer_cb_.Run(start_dts, start_pts);
 
   base::AutoLock auto_lock(lock_);
-  stream_->OnStartOfCodedFrameGroup(start_dts, start_pts);
+  stream_->OnStartOfCodedFrameGroup(start_pts);
 }
 
 bool ChunkDemuxerStream::UpdateAudioConfig(const AudioDecoderConfig& config,
@@ -808,11 +805,9 @@ void ChunkDemuxer::OnMemoryPressure(
     base::TimeDelta currentMediaTime,
     base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level,
     bool force_instant_gc) {
-  DecodeTimestamp media_time_dts =
-      DecodeTimestamp::FromPresentationTime(currentMediaTime);
   base::AutoLock auto_lock(lock_);
   for (const auto& itr : source_state_map_) {
-    itr.second->OnMemoryPressure(media_time_dts, memory_pressure_level,
+    itr.second->OnMemoryPressure(currentMediaTime, memory_pressure_level,
                                  force_instant_gc);
   }
 }

media/filters/chunk_demuxer.h

@@ -72,7 +72,7 @@ class MEDIA_EXPORT ChunkDemuxerStream : public DemuxerStream {
   bool EvictCodedFrames(base::TimeDelta media_time, size_t newDataSize);
 
   void OnMemoryPressure(
-      DecodeTimestamp media_time,
+      base::TimeDelta media_time,
       base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level,
       bool force_instant_gc);
 
@@ -94,8 +94,10 @@ class MEDIA_EXPORT ChunkDemuxerStream : public DemuxerStream {
   size_t GetBufferedSize() const;
 
   // Signal to the stream that buffers handed in through subsequent calls to
-  // Append() belong to a coded frame group that starts at |start_dts| and
-  // |start_pts|.
+  // Append() belong to a coded frame group that starts at |start_pts|.
+  // |start_dts| is used only to help tests verify correctness of calls to this
+  // method. If |group_start_observer_cb_| is set, first invokes this test-only
+  // callback with |start_dts| and |start_pts| to assist test verification.
   void OnStartOfCodedFrameGroup(DecodeTimestamp start_dts,
                                 base::TimeDelta start_pts);
 
@@ -173,6 +175,8 @@ class MEDIA_EXPORT ChunkDemuxerStream : public DemuxerStream {
 
   const MediaTrack::Id media_track_id_;
 
+  // Test-only callbacks to assist verification of Append() and
+  // OnStartOfCodedFrameGroup() calls, respectively.
   AppendObserverCB append_observer_cb_;
   GroupStartObserverCB group_start_observer_cb_;
 

media/filters/source_buffer_state.cc

@@ -313,7 +313,7 @@ bool SourceBufferState::EvictCodedFrames(base::TimeDelta media_time,
 }
 
 void SourceBufferState::OnMemoryPressure(
-    DecodeTimestamp media_time,
+    base::TimeDelta media_time,
     base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level,
     bool force_instant_gc) {
   // Notify video streams about memory pressure first, since video typically

media/filters/source_buffer_state.h

@@ -86,11 +86,11 @@ class MEDIA_EXPORT SourceBufferState {
   // Gets invoked when the system is experiencing memory pressure, i.e. there's
   // not enough free memory. The |media_time| is the media playback position at
   // the time of memory pressure notification (needed for accurate GC). The
-  // |memory_pressure_listener| indicates memory pressure severity. The
+  // |memory_pressure_level| indicates memory pressure severity. The
   // |force_instant_gc| is used to force the MSE garbage collection algorithm to
   // be run right away, without waiting for the next append.
   void OnMemoryPressure(
-      DecodeTimestamp media_time,
+      base::TimeDelta media_time,
       base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level,
       bool force_instant_gc);