From fb3387d7969be63e771c3a1b018e1ee9674e2b2b Mon Sep 17 00:00:00 2001
From: Paul Adenot <paul@paul.cx>
Date: Mon, 19 Oct 2020 08:45:04 +0000
Subject: [PATCH] Bug 1346880 - Always initialize an AudioChannelAgent when
 initializing an AudioContext. r=alwu

Differential Revision: https://phabricator.services.mozilla.com/D92644
---
 dom/media/webaudio/AudioContext.cpp         |  1 +
 dom/media/webaudio/AudioDestinationNode.cpp | 12 ++++++++++++
 dom/media/webaudio/AudioDestinationNode.h   |  2 ++
 3 files changed, 15 insertions(+)

diff --git a/dom/media/webaudio/AudioContext.cpp b/dom/media/webaudio/AudioContext.cpp
index c2991598ab26..df6fa6687009 100644
--- a/dom/media/webaudio/AudioContext.cpp
+++ b/dom/media/webaudio/AudioContext.cpp
@@ -176,6 +176,7 @@ AudioContext::AudioContext(nsPIDOMWindowInner* aWindow, bool aIsOffline,
   const bool allowedToStart = AutoplayPolicy::IsAllowedToPlay(*this);
   mDestination = new AudioDestinationNode(this, aIsOffline, allowedToStart,
                                           aNumberOfChannels, aLength);
+  mDestination->Init();
   // If an AudioContext is not allowed to start, we would postpone its state
   // transition from `suspended` to `running` until sites explicitly call
   // AudioContext.resume() or AudioScheduledSourceNode.start().
diff --git a/dom/media/webaudio/AudioDestinationNode.cpp b/dom/media/webaudio/AudioDestinationNode.cpp
index 04da4a09a7c8..17cdeb86c629 100644
--- a/dom/media/webaudio/AudioDestinationNode.cpp
+++ b/dom/media/webaudio/AudioDestinationNode.cpp
@@ -321,6 +321,18 @@ AudioDestinationNode::AudioDestinationNode(AudioContext* aContext,
   }
 }
 
+void AudioDestinationNode::Init() {
+  if (!mIsOffline) {
+    CreateAudioChannelAgent();
+    nsresult rv = mAudioChannelAgent->NotifyStartedPlaying(
+        AudioChannelService::AudibleState::eNotAudible);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return;
+    }
+    mAudioChannelAgent->PullInitialUpdate();
+  }
+}
+
 AudioDestinationNode::~AudioDestinationNode() {
   ReleaseAudioWakeLockIfExists();
 }
diff --git a/dom/media/webaudio/AudioDestinationNode.h b/dom/media/webaudio/AudioDestinationNode.h
index 9066b1145cfb..f2cdc70e1984 100644
--- a/dom/media/webaudio/AudioDestinationNode.h
+++ b/dom/media/webaudio/AudioDestinationNode.h
@@ -42,6 +42,8 @@ class AudioDestinationNode final : public AudioNode,
   uint32_t MaxChannelCount() const;
   void SetChannelCount(uint32_t aChannelCount, ErrorResult& aRv) override;
 
+  void Init();
+
   // Returns the track or null after unlink.
   AudioNodeTrack* Track();