Reland: MediaCaptureFromElement: add support for audio captureStream().

media/blink/webaudiosourceprovider_impl.cc

Index: media/blink/webaudiosourceprovider_impl.cc
diff --git a/media/blink/webaudiosourceprovider_impl.cc b/media/blink/webaudiosourceprovider_impl.cc
index 3f052dbeb6f5a8f9759964cb534635f5e19ebd79..b2b04e834c8c19f76d38ea48280cab498664cf69 100644
--- a/media/blink/webaudiosourceprovider_impl.cc
+++ b/media/blink/webaudiosourceprovider_impl.cc
@@ -50,18 +50,22 @@ class AutoTryLock {
 
 // TeeFilter is a RenderCallback implementation that allows for a client to get
 // a copy of the data being rendered by the |renderer_| on Render(). This class
-// also holds to the necessary audio parameters.
+// also holds on to the necessary audio parameters.
 class WebAudioSourceProviderImpl::TeeFilter
     : public AudioRendererSink::RenderCallback {
  public:
-  TeeFilter(AudioRendererSink::RenderCallback* renderer,
-            int channels,
-            int sample_rate)
-      : renderer_(renderer), channels_(channels), sample_rate_(sample_rate) {
-    DCHECK(renderer_);
-  }
+  TeeFilter() : renderer_(nullptr), channels_(0), sample_rate_(0) {}
   ~TeeFilter() override {}
 
+  void Initialize(AudioRendererSink::RenderCallback* renderer,
+                  int channels,
+                  int sample_rate) {
+    DCHECK(renderer);
+    renderer_ = renderer;
+    channels_ = channels;
+    sample_rate_ = sample_rate;
+  }
+
   // AudioRendererSink::RenderCallback implementation.
   // These are forwarders to |renderer_| and are here to allow for a client to
   // get a copy of the rendered audio by SetCopyAudioCallback().
@@ -70,19 +74,19 @@ class WebAudioSourceProviderImpl::TeeFilter
              uint32_t frames_skipped) override;
   void OnRenderError() override;
 
+  bool IsInitialized() const { return !!renderer_; }
   int channels() const { return channels_; }
   int sample_rate() const { return sample_rate_; }
-  void set_copy_audio_bus_callback(
-      const WebAudioSourceProviderImpl::CopyAudioCB& callback) {
+  void set_copy_audio_bus_callback(const CopyAudioCB& callback) {
     copy_audio_bus_callback_ = callback;
   }
 
  private:
-  AudioRendererSink::RenderCallback* const renderer_;
-  const int channels_;
-  const int sample_rate_;
+  AudioRendererSink::RenderCallback* renderer_;
+  int channels_;
+  int sample_rate_;
 
-  WebAudioSourceProviderImpl::CopyAudioCB copy_audio_bus_callback_;
+  CopyAudioCB copy_audio_bus_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(TeeFilter);
 };
@@ -93,6 +97,7 @@ WebAudioSourceProviderImpl::WebAudioSourceProviderImpl(
       state_(kStopped),
       client_(nullptr),
       sink_(sink),
+      tee_filter_(new TeeFilter()),
       weak_factory_(this) {}
 
 WebAudioSourceProviderImpl::~WebAudioSourceProviderImpl() {
@@ -111,12 +116,11 @@ void WebAudioSourceProviderImpl::setClient(
     set_format_cb_ = BindToCurrentLoop(base::Bind(
         &WebAudioSourceProviderImpl::OnSetFormat, weak_factory_.GetWeakPtr()));
 
-    // If |tee_filter_| is set, it means we have been Initialize()d - then run
-    // |set_format_cb_| to send |client_| the current format info. Otherwise
-    // |set_format_cb_| will get called when Initialize() is called.
-    // Note: Always using |set_format_cb_| ensures we have the same locking
-    // order when calling into |client_|.
-    if (tee_filter_)
+    // If |tee_filter_| is Initialize()d - then run |set_format_cb_| to send
+    // |client_| the current format info. Otherwise |set_format_cb_| will get
+    // called when Initialize() is called. Note: Always using |set_format_cb_|
+    // ensures we have the same locking order when calling into |client_|.
+    if (tee_filter_->IsInitialized())  // ???

[DaleCurtis, 2016/05/23 18:37:18]

Remove ???

[mcasas, 2016/05/23 19:00:13]

Done.

       base::ResetAndReturn(&set_format_cb_).Run();
   } else if (!client && client_) {
     // Restore normal playback.
@@ -151,7 +155,6 @@ void WebAudioSourceProviderImpl::provideInput(
   }
 
   DCHECK(client_);
-  DCHECK(tee_filter_);
   DCHECK_EQ(tee_filter_->channels(), bus_wrapper_->channels());
   const int frames = tee_filter_->Render(bus_wrapper_.get(), 0, 0);
   if (frames < incoming_number_of_frames)
@@ -221,8 +224,7 @@ void WebAudioSourceProviderImpl::Initialize(const AudioParameters& params,
   base::AutoLock auto_lock(sink_lock_);
   DCHECK_EQ(state_, kStopped);
 
-  tee_filter_ = base::WrapUnique(
-      new TeeFilter(renderer, params.channels(), params.sample_rate()));
+  tee_filter_->Initialize(renderer, params.channels(), params.sample_rate());
 
   sink_->Initialize(params, tee_filter_.get());
 
@@ -233,6 +235,10 @@ void WebAudioSourceProviderImpl::Initialize(const AudioParameters& params,
 void WebAudioSourceProviderImpl::SetCopyAudioCallback(
     const CopyAudioCB& callback) {
   DCHECK(!callback.is_null());
+
+  // Use |sink_lock_| to protect |tee_filter_| too since they go in lockstep.
+  base::AutoLock auto_lock(sink_lock_);
+
   DCHECK(tee_filter_);
   tee_filter_->set_copy_audio_bus_callback(callback);
 }
@@ -242,6 +248,10 @@ void WebAudioSourceProviderImpl::ClearCopyAudioCallback() {
   tee_filter_->set_copy_audio_bus_callback(CopyAudioCB());
 }
 
+int WebAudioSourceProviderImpl::RenderForTesting(AudioBus* audio_bus) {
+  return tee_filter_->Render(audio_bus, 0, 0);
+}
+
 void WebAudioSourceProviderImpl::OnSetFormat() {
   base::AutoLock auto_lock(sink_lock_);
   if (!client_)
@@ -251,13 +261,12 @@ void WebAudioSourceProviderImpl::OnSetFormat() {
   client_->setFormat(tee_filter_->channels(), tee_filter_->sample_rate());
 }
 
-int WebAudioSourceProviderImpl::RenderForTesting(AudioBus* audio_bus) {
-  return tee_filter_->Render(audio_bus, 0, 0);
-}
-
 int WebAudioSourceProviderImpl::TeeFilter::Render(AudioBus* audio_bus,
                                                   uint32_t delay_milliseconds,
                                                   uint32_t frames_skipped) {
+  if (!renderer_)

[DaleCurtis, 2016/05/23 18:37:18]

This should be impossible, no?

[mcasas, 2016/05/23 19:00:13]

It could be possible if we get data before the
|renderer_| has been set, but seeing your reaction
I believe is is enforced in the class contract. 
Changed for a DCHECK.

+    return 0;
+
   const int num_rendered_frames =
       renderer_->Render(audio_bus, delay_milliseconds, frames_skipped);
 
@@ -273,7 +282,8 @@ int WebAudioSourceProviderImpl::TeeFilter::Render(AudioBus* audio_bus,
 }
 
 void WebAudioSourceProviderImpl::TeeFilter::OnRenderError() {
-  renderer_->OnRenderError();
+  if (renderer_)

[DaleCurtis, 2016/05/23 18:37:18]

Ditto.

[mcasas, 2016/05/23 19:00:13]

Acknowledged.

+    renderer_->OnRenderError();
 }
 
 }  // namespace media