Experiment with more aggressive MSE GC on memory pressure

media/filters/source_buffer_stream.h

Index: media/filters/source_buffer_stream.h
diff --git a/media/filters/source_buffer_stream.h b/media/filters/source_buffer_stream.h
index 566477b81bd1120654d65221e9bd2885727aabd8..0a3f0236d6078dfd3a222b70cf9375a5560ec2d1 100644
--- a/media/filters/source_buffer_stream.h
+++ b/media/filters/source_buffer_stream.h
@@ -19,6 +19,7 @@
 #include <vector>
 
 #include "base/macros.h"
+#include "base/memory/memory_pressure_listener.h"
 #include "base/memory/ref_counted.h"
 #include "media/base/audio_decoder_config.h"
 #include "media/base/media_export.h"
@@ -93,6 +94,17 @@ class MEDIA_EXPORT SourceBufferStream {
   bool GarbageCollectIfNeeded(DecodeTimestamp media_time,
                               size_t newDataSize);
 
+  // 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
+  // |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::MemoryPressureListener::MemoryPressureLevel memory_pressure_level,
+      bool force_instant_gc);
+
   // Changes the SourceBufferStream's state so that it will start returning
   // buffers starting from the closest keyframe before |timestamp|.
   void Seek(base::TimeDelta timestamp);
@@ -430,6 +442,9 @@ class MEDIA_EXPORT SourceBufferStream {
   // Stores the largest distance between two adjacent buffers in this stream.
   base::TimeDelta max_interbuffer_distance_;
 
+  base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level_ =
+      base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE;
+
   // The maximum amount of data in bytes the stream will keep in memory.
   size_t memory_limit_;