Bug 1184058 - AudioChannelAgent should be muted when used without a proper window object, r=alwu

dom/audiochannel/AudioChannelAgent.cpp

@@ -85,6 +85,8 @@ AudioChannelAgent::InitInternal(nsIDOMWindow* aWindow, int32_t aChannelType,
                                 nsIAudioChannelAgentCallback *aCallback,
                                 bool aUseWeakRef)
 {
+  MOZ_ASSERT(aWindow);
+
   // We syncd the enum of channel type between nsIAudioChannelAgent.idl and
   // AudioChannelBinding.h the same.
   MOZ_ASSERT(int(AUDIO_AGENT_CHANNEL_NORMAL) == int(AudioChannel::Normal) &&
@@ -103,17 +105,19 @@ AudioChannelAgent::InitInternal(nsIDOMWindow* aWindow, int32_t aChannelType,
     return NS_ERROR_FAILURE;
   }
 
-  if (aWindow) {
-    nsCOMPtr<nsPIDOMWindow> pInnerWindow = do_QueryInterface(aWindow);
-    MOZ_ASSERT(pInnerWindow->IsInnerWindow());
-    mInnerWindowID = pInnerWindow->WindowID();
+  nsCOMPtr<nsPIDOMWindow> pInnerWindow = do_QueryInterface(aWindow);
+  MOZ_ASSERT(pInnerWindow->IsInnerWindow());
+  mInnerWindowID = pInnerWindow->WindowID();
 
-    nsCOMPtr<nsIDOMWindow> topWindow;
-    aWindow->GetScriptableTop(getter_AddRefs(topWindow));
-    mWindow = do_QueryInterface(topWindow);
-    if (mWindow) {
-      mWindow = mWindow->GetOuterWindow();
-    }
+  nsCOMPtr<nsIDOMWindow> topWindow;
+  aWindow->GetScriptableTop(getter_AddRefs(topWindow));
+  mWindow = do_QueryInterface(topWindow);
+  if (mWindow) {
+    mWindow = mWindow->GetOuterWindow();
+  }
+
+  if (!mWindow) {
+    return NS_ERROR_FAILURE;
   }
 
   mAudioChannelType = aChannelType;
@@ -134,6 +138,13 @@ NS_IMETHODIMP AudioChannelAgent::NotifyStartedPlaying(uint32_t aNotifyPlayback,
   MOZ_ASSERT(aVolume);
   MOZ_ASSERT(aMuted);
 
+  // Window-less AudioChannelAgents are muted by default.
+  if (!mWindow) {
+    *aVolume = 0;
+    *aMuted = true;
+    return NS_OK;
+  }
+
   nsRefPtr<AudioChannelService> service = AudioChannelService::GetOrCreate();
   if (mAudioChannelType == AUDIO_AGENT_CHANNEL_ERROR ||
       service == nullptr || mIsRegToService) {