Bug 1133449 - [B2G] The default audio type didn't be set correctly when the call screen app is launched. r=baku

dom/audiochannel/AudioChannelService.cpp

@@ -525,15 +525,26 @@ AudioChannelService::SetDefaultVolumeControlChannelInternal(int32_t aChannel,
   // If this child is in the background and mDefChannelChildID is set to
   // others then it means other child in the foreground already set it's
   // own default channel already.
-  if ((!aVisible && mDefChannelChildID != aChildID) ||
-      (mDefChannelChildID != aChildID &&
-       mDefChannelChildID != CONTENT_PROCESS_ID_UNKNOWN)) {
+  if (!aVisible && mDefChannelChildID != aChildID) {
+    return;
+  }
+  // Workaround for the call screen app. The call screen app is running on the
+  // main process, that will results in wrong visible state. Because we use the
+  // docshell's active state as visible state, the main process is always
+  // active. Therefore, we will see the strange situation that the visible
+  // state of the call screen is always true. If the mDefChannelChildID is set
+  // to others then it means other child in the foreground already set it's
+  // own default channel already.
+  // Summary :
+  //   Child process : foreground app always can set type.
+  //   Parent process : check the mDefChannelChildID.
+  else if (aChildID == CONTENT_PROCESS_ID_MAIN &&
+           mDefChannelChildID != CONTENT_PROCESS_ID_UNKNOWN) {
     return;
   }
 
-  mDefChannelChildID = aChildID;
-  nsString channelName;
-
+  mDefChannelChildID = aVisible ? aChildID : CONTENT_PROCESS_ID_UNKNOWN;
+  nsAutoString channelName;
   if (aChannel == -1) {
     channelName.AssignASCII("unknown");
   } else {