Experiment with more aggressive MSE GC on memory pressure

media/blink/webmediaplayer_impl.cc

Index: media/blink/webmediaplayer_impl.cc
diff --git a/media/blink/webmediaplayer_impl.cc b/media/blink/webmediaplayer_impl.cc
index aabb04079f5861bd4dd8c600c9dab1a20ae6ada7..98f8b3119d127252384aa673de59ce9f1b9b1a8f 100644
--- a/media/blink/webmediaplayer_impl.cc
+++ b/media/blink/webmediaplayer_impl.cc
@@ -18,6 +18,7 @@
 #include "base/debug/alias.h"
 #include "base/debug/crash_logging.h"
 #include "base/location.h"
+#include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_number_conversions.h"
@@ -1173,6 +1174,22 @@ void WebMediaPlayerImpl::OnDemuxerOpened() {
       new WebMediaSourceImpl(chunk_demuxer_, media_log_));
 }
 
+void WebMediaPlayerImpl::OnMemoryPressure(
+    base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level) {
+  DVLOG(2) << __func__ << " memory_pressure_level=" << memory_pressure_level;
+  DCHECK(main_task_runner_->BelongsToCurrentThread());
+  DCHECK(base::FeatureList::IsEnabled(kReduceMSEBuffersOnMemoryPressure));
+  if (chunk_demuxer_) {
+    // base::Unretained is safe, since chunk_demuxer_ is actually owned by
+    // |this| via this->demuxer_.
+    media_task_runner_->PostTask(
+        FROM_HERE, base::Bind(&ChunkDemuxer::OnMemoryPressure,
+                              base::Unretained(chunk_demuxer_),
+                              base::TimeDelta::FromSecondsD(currentTime()),
+                              memory_pressure_level));
+  }
+}
+
 void WebMediaPlayerImpl::OnError(PipelineStatus status) {
   DVLOG(1) << __func__;
   DCHECK(main_task_runner_->BelongsToCurrentThread());
@@ -1726,6 +1743,13 @@ void WebMediaPlayerImpl::StartPipeline() {
   // TODO(sandersd): On Android, defer Start() if the tab is not visible.
   seeking_ = true;
   pipeline_controller_.Start(demuxer_.get(), this, is_streaming, is_static);
+
+  if (base::FeatureList::IsEnabled(kReduceMSEBuffersOnMemoryPressure)) {
+    // base::Unretained is safe because |this| owns memory_pressure_listener_.
+    memory_pressure_listener_ =

[chcunningham, 2017/01/25 03:47:15]

Do we want to make a new one every time the pipeline gets started? (e.g. if
someone calls load() more than once?). why not constructor?

Also, do you want to bother creating it when not media source?

[servolk, 2017/01/25 18:06:47]

I guess I wanted to avoid having the overhead of memory listener if a media
element is created, but not started. E.g. if there's a <video> element in the
page, but it's not autoplay.
But it's not a big deal, I guess. We can move it to where we are creating the
|chunk_demuxer_| for now.

[chcunningham, 2017/01/25 22:21:56]

Acknowledged.

+        base::MakeUnique<base::MemoryPressureListener>(base::Bind(
+            &WebMediaPlayerImpl::OnMemoryPressure, base::Unretained(this)));
+  }
 }
 
 void WebMediaPlayerImpl::SetNetworkState(WebMediaPlayer::NetworkState state) {