Revert of Remove dangling PlayingState pointers in WebRtcAudioRenderer....

Revert of Remove dangling PlayingState pointers in WebRtcAudioRenderer. (patchset #4 id:60001 of https://codereview.chromium.org/2758453004/ )

Reason for revert:
This causes a memory use increase across the board on Android, even when WebRTC isn't used.

Original issue's description:
> Remove dangling PlayingState pointers in WebRtcAudioRenderer.
>
> This solution is a bit of a hack, but it works. Did manual testing and ran
> unit tests. Bug 697256 does not reproduce with this patch.
>
> R=tommi@chromium.org
>
> BUG=697256
>
> Review-Url: https://codereview.chromium.org/2758453004
> Cr-Commit-Position: refs/heads/master@{#458025}
> Committed: https://chromium.googlesource.com/chromium/src/+/ba21ffd704aebcc8a5e5e1ab1f072e9b79b51fcb

TBR=tommi@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=697256,703743

Review-Url: https://codereview.chromium.org/2856943003
Cr-Commit-Position: refs/heads/master@{#468984}

content/renderer/media/webrtc_audio_renderer.cc

@@ -54,24 +54,17 @@ class SharedAudioRenderer : public MediaStreamAudioRenderer {
  public:
   // Callback definition for a callback that is called when when Play(), Pause()
   // or SetVolume are called (whenever the internal |playing_state_| changes).
-  using OnPlayStateChanged =
-      base::Callback<void(const blink::WebMediaStream&,
-                          WebRtcAudioRenderer::PlayingState*)>;
-
-  // Signals that the PlayingState* is about to become invalid, see comment in
-  // OnPlayStateRemoved.
-  using OnPlayStateRemoved =
-      base::OnceCallback<void(WebRtcAudioRenderer::PlayingState*)>;
+  typedef base::Callback<void(const blink::WebMediaStream&,
+                              WebRtcAudioRenderer::PlayingState*)>
+      OnPlayStateChanged;
 
   SharedAudioRenderer(const scoped_refptr<MediaStreamAudioRenderer>& delegate,
                       const blink::WebMediaStream& media_stream,
-                      const OnPlayStateChanged& on_play_state_changed,
-                      OnPlayStateRemoved on_play_state_removed)
+                      const OnPlayStateChanged& on_play_state_changed)
       : delegate_(delegate),
         media_stream_(media_stream),
         started_(false),
-        on_play_state_changed_(on_play_state_changed),
-        on_play_state_removed_(std::move(on_play_state_removed)) {
+        on_play_state_changed_(on_play_state_changed) {
     DCHECK(!on_play_state_changed_.is_null());
     DCHECK(!media_stream_.IsNull());
   }
@@ -81,7 +74,6 @@ class SharedAudioRenderer : public MediaStreamAudioRenderer {
     DCHECK(thread_checker_.CalledOnValidThread());
     DVLOG(1) << __func__;
     Stop();
-    std::move(on_play_state_removed_).Run(&playing_state_);
   }
 
   void Start() override {
@@ -156,7 +148,6 @@ class SharedAudioRenderer : public MediaStreamAudioRenderer {
   bool started_;
   WebRtcAudioRenderer::PlayingState playing_state_;
   OnPlayStateChanged on_play_state_changed_;
-  OnPlayStateRemoved on_play_state_removed_;
 };
 
 }  // namespace
@@ -229,12 +220,9 @@ bool WebRtcAudioRenderer::Initialize(WebRtcAudioRendererSource* source) {
 scoped_refptr<MediaStreamAudioRenderer>
 WebRtcAudioRenderer::CreateSharedAudioRendererProxy(
     const blink::WebMediaStream& media_stream) {
-  SharedAudioRenderer::OnPlayStateChanged on_play_state_changed =
+  content::SharedAudioRenderer::OnPlayStateChanged on_play_state_changed =
       base::Bind(&WebRtcAudioRenderer::OnPlayStateChanged, this);
-  SharedAudioRenderer::OnPlayStateRemoved on_play_state_removed =
-      base::BindOnce(&WebRtcAudioRenderer::OnPlayStateRemoved, this);
-  return new SharedAudioRenderer(this, media_stream, on_play_state_changed,
-                                 std::move(on_play_state_removed));
+  return new SharedAudioRenderer(this, media_stream, on_play_state_changed);
 }
 
 bool WebRtcAudioRenderer::IsStarted() const {
@@ -605,27 +593,6 @@ void WebRtcAudioRenderer::OnPlayStateChanged(
   }
 }
 
-void WebRtcAudioRenderer::OnPlayStateRemoved(PlayingState* state) {
-  // It is possible we associated |state| to a source for a track that is no
-  // longer easily reachable. We iterate over |source_playing_states_| to
-  // ensure there are no dangling pointers to |state| there. See
-  // crbug.com/697256.
-  // TODO(maxmorin): Clean up cleanup code in this and related classes so that
-  // this hack isn't necessary.
-  DCHECK(thread_checker_.CalledOnValidThread());
-  for (auto it = source_playing_states_.begin();
-       it != source_playing_states_.end();) {
-    PlayingStates& states = it->second;
-    // We cannot use RemovePlayingState as it might invalidate |it|.
-    states.erase(std::remove(states.begin(), states.end(), state),
-                 states.end());
-    if (states.empty())
-      it = source_playing_states_.erase(it);
-    else
-      ++it;
-  }
-}
-
 void WebRtcAudioRenderer::PrepareSink() {
   DCHECK(thread_checker_.CalledOnValidThread());
   media::AudioParameters new_sink_params;

content/renderer/media/webrtc_audio_renderer.h

@@ -8,7 +8,6 @@
 #include <stdint.h>
 
 #include <map>
-#include <memory>
 #include <string>
 #include <vector>
 
@@ -194,9 +193,6 @@ class CONTENT_EXPORT WebRtcAudioRenderer
   void OnPlayStateChanged(const blink::WebMediaStream& media_stream,
                           PlayingState* state);
 
-  // Called when |state| is about to be destructed.
-  void OnPlayStateRemoved(PlayingState* state);
-
   // Updates |sink_params_| and |audio_fifo_| based on |sink_|, and initializes
   // |sink_|.
   void PrepareSink();