Expand suspension of idle media players to all platforms.

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 07e2aadac855b420f781d15b859853d00feee4df..1265c3ca12fe0a73a6f18bf5c1535d55157b8020 100644
--- a/media/blink/webmediaplayer_impl.cc
+++ b/media/blink/webmediaplayer_impl.cc
@@ -105,6 +105,17 @@ void SetSinkIdOnMediaThread(scoped_refptr<WebAudioSourceProviderImpl> sink,
   }
 }
 
+bool IsSuspendUponHiddenEnabled() {
+#if !defined(OS_ANDROID)
+  // Suspend/Resume is only enabled by default on Android.
+  return base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableMediaSuspend);
+#else
+  return !base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kDisableMediaSuspend);
+#endif
+}
+
 }  // namespace
 
 class BufferedDataSourceHostImpl;
@@ -339,6 +350,7 @@ void WebMediaPlayerImpl::play() {
   }
 #endif
 
+  const bool was_paused = paused_;
   paused_ = false;
   pipeline_.SetPlaybackRate(playback_rate_);
 
@@ -347,13 +359,13 @@ void WebMediaPlayerImpl::play() {
 
   media_log_->AddEvent(media_log_->CreateEvent(MediaLogEvent::PLAY));
 
-  if (playback_rate_ > 0) {
+  if (playback_rate_ > 0 && was_paused) {
     NotifyPlaybackStarted();
 
-    // Resume the player if playback was initiated in the foreground. Resume()
-    // will do nothing if the pipeline is not suspended state, but will clear
-    // some internal pending state, so it should always be called.
-    if (delegate_ && !delegate_->IsHidden())
+    // Resume the player if allowed. We always call Resume() in case there is a
+    // pending suspend that should be aborted. If the pipeline is not suspended,
+    // Resume() will have no effect.
+    if (IsAutomaticResumeAllowed())
       pipeline_controller_.Resume();
   }
 }
@@ -442,10 +454,10 @@ void WebMediaPlayerImpl::DoSeek(base::TimeDelta time, bool time_updated) {
     paused_time_ = time;
   pipeline_controller_.Seek(time, time_updated);
 
-  // Resume the pipeline if the seek is initiated in the foreground so that
-  // the correct frame is displayed. If the pipeline is not suspended, Resume()
-  // will do nothing but clear some pending state.
-  if (delegate_ && !delegate_->IsHidden())
+  // Resume the pipeline if allowed so that the correct frame is displayed. We
+  // always call Resume() in case there is a pending suspend that should be
+  // aborted. If the pipeline is not suspended, Resume() will have no effect.
+  if (IsAutomaticResumeAllowed())
     pipeline_controller_.Resume();
 }
 
@@ -858,8 +870,6 @@ void WebMediaPlayerImpl::OnPipelineSuspended() {
   }
 #endif
 
-  if (delegate_)
-    delegate_->PlayerGone(delegate_id_);
   memory_usage_reporting_timer_.Stop();
   ReportMemoryUsage();
 
@@ -871,8 +881,13 @@ void WebMediaPlayerImpl::OnPipelineSuspended() {
 }
 
 void WebMediaPlayerImpl::OnPipelineResumed() {
-  if (playback_rate_ > 0 && !paused_)
+  if (playback_rate_ > 0 && !paused_) {
     NotifyPlaybackStarted();
+  } else if (!playback_rate_ || paused_ || ended_) {
+    // Resend our paused notification so the pipeline is considered for idle
+    // resource reclamation; duplicate pause notifications are ignored.
+    NotifyPlaybackPaused();
+  }
 }
 
 void WebMediaPlayerImpl::OnPipelineEnded() {
@@ -936,7 +951,7 @@ void WebMediaPlayerImpl::OnPipelineMetadata(
     // If there is video and the frame is hidden, then it may be time to suspend
     // playback.
     if (delegate_ && delegate_->IsHidden())
-      OnHidden(false);
+      OnHidden();
   }
 }
 
@@ -997,49 +1012,35 @@ void WebMediaPlayerImpl::OnAddTextTrack(
   done_cb.Run(std::move(text_track));
 }
 
-void WebMediaPlayerImpl::OnHidden(bool must_suspend) {
+void WebMediaPlayerImpl::OnHidden() {
   DCHECK(main_task_runner_->BelongsToCurrentThread());
-
-#if !defined(OS_ANDROID)
-  // Suspend/Resume is enabled by default on Android.
-  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableMediaSuspend)) {
+  if (!IsSuspendUponHiddenEnabled())
     return;
-  }
-#endif  // !defined(OS_ANDROID)
 
-  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kDisableMediaSuspend)) {
-    return;
-  }
-
-#if defined(OS_ANDROID)
+#if defined(OS_ANDROID)  // WMPI_CAST
   // If we're remote, the pipeline should already be suspended.
   if (isRemote())
     return;
 #endif
 
-  if (must_suspend || (paused_ && ended_) || hasVideo())
-    pipeline_controller_.Suspend();
+  // Don't suspend players which only have audio and have not completed
+  // playback. The user can still control these players via the MediaSession UI.
+  // If the player has never started playback, OnSuspendRequested() will handle
+  // release of any idle resources.
+  if (!hasVideo() && !paused_ && !ended_)
+    return;
+
+  pipeline_controller_.Suspend();
+  if (delegate_)

[xhwang, 2016/03/10 21:51:06]

One comment about the |delegate_|:

We are storing the |delegate_| as a weak pointer and checking it everywhere we
use it. This is probably not necessary.

The delegate is kinda owned by RenderFrameImpl [1]. And HTMLMediaElement is an
ActiveDOMObject. ActiveDOMObject::stop() is guaranteed to be called before a
frame is detached, so it's impossible for WMPI to outlive the frame and
dereference a destructed delegate. You can see a similar discussion at [2].

If that makes sense, we can do some clean up around the |delegate_|:
1. Pass and store |delegate_| as a raw pointer.
2. Remove all the if(delegate_) check in WMP implementations.
3. (optional) Drop the RenderFrameObserver base class for
RendererWebMediaPlayerDelegate and store |media_player_delegate_| as a normal
scoped_ptr member in RenderFrameImpl.

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/content/renderer/r...
[2] https://codereview.chromium.org/1464183002/#msg42

[DaleCurtis, 2016/03/10 23:11:36]

Yay! Thanks for this, I was hoping this was possible, but hadn't dug into it
deep enough yet. I'll do that in a follow up CL.  Filed http://crbug.com/593932

+    delegate_->PlayerGone(delegate_id_);
 }
 
 void WebMediaPlayerImpl::OnShown() {
   DCHECK(main_task_runner_->BelongsToCurrentThread());
-
-#if !defined(OS_ANDROID)
-  // Suspend/Resume is enabled by default on Android.
-  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableMediaSuspend)) {
+  if (!IsSuspendUponHiddenEnabled())
     return;
-  }
-#endif  // !defined(OS_ANDROID)
-
-  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kDisableMediaSuspend)) {
-    return;
-  }
 
-#if defined(OS_ANDROID)
+#if defined(OS_ANDROID)  // WMPI_CAST
   // If we're remote, the pipeline should stay suspended.
   if (isRemote())
     return;
@@ -1049,6 +1050,27 @@ void WebMediaPlayerImpl::OnShown() {
     pipeline_controller_.Resume();
 }
 
+void WebMediaPlayerImpl::OnSuspendRequested(bool must_suspend) {
+  DCHECK(main_task_runner_->BelongsToCurrentThread());
+
+#if defined(OS_ANDROID)  // WMPI_CAST
+  // If we're remote, the pipeline should already be suspended.
+  if (isRemote())
+    return;
+#endif
+
+  // Suspend should never be requested unless required or we're already in an
+  // idle state (paused or ended).
+  DCHECK(must_suspend || paused_ || ended_);
+
+  // Always suspend, but only notify the delegate if we must; this allows any
+  // exposed UI for player controls to continue to function even though the
+  // player has now been suspended.

[xhwang, 2016/03/10 21:51:06]

The comment on the API says:

// Requests a WebMediaPlayer instance to release all idle resources. If
// |must_suspend| is false, the player may ignore the request. However, if
// |must_suspend| is true, the player must stop playback, release all
// resources, and finally call WebMediaPlayerDelegate::PlayerGone().

It's not clear whether we should call PlayerGone() when |must_suspend| is false.

Then the comment on PlayerGone() says:

// The specified player was destroyed or suspended...

In this case, the player IS suspended, so it seems we should call PlayerGone()
in all cases...

I kinda feel we need some more clarification on the API.

[DaleCurtis, 2016/03/10 23:11:36]

I thought it was pretty clear, but I've filled out the comments a bit more :)

+  pipeline_controller_.Suspend();
+  if (must_suspend && delegate_)
+    delegate_->PlayerGone(delegate_id_);
+}
+
 void WebMediaPlayerImpl::OnPlay() {
   play();
   client_->playbackStateChanged();
@@ -1430,4 +1452,13 @@ void WebMediaPlayerImpl::FinishMemoryUsageReport(int64_t demuxer_memory_usage) {
   adjust_allocated_memory_cb_.Run(delta);
 }
 
+bool WebMediaPlayerImpl::IsAutomaticResumeAllowed() {
+#if defined(OS_ANDROID)
+  return !hasVideo() || (delegate_ && !delegate_->IsHidden());
+#else
+  // On non-Android platforms Resume() is always allowed.
+  return true;
+#endif
+}
+
 }  // namespace media