Restores larger output buffer size when output stream requiring smaller size is closed

media/audio/mac/audio_manager_mac.h

Index: media/audio/mac/audio_manager_mac.h
diff --git a/media/audio/mac/audio_manager_mac.h b/media/audio/mac/audio_manager_mac.h
index f5159e956cc44a249af38a698cf4e3399969f6b5..7c9823931a78475eaed1e14adeab9c2a585fd3ed 100644
--- a/media/audio/mac/audio_manager_mac.h
+++ b/media/audio/mac/audio_manager_mac.h
@@ -111,6 +111,12 @@ class MEDIA_EXPORT AudioManagerMac : public AudioManagerBase {
   }
   size_t basic_input_streams() const { return basic_input_streams_.size(); }
 
+#if !defined(NDEBUG)
+  // Prints a list of all existing output streams and there current buffer size
+  // state (required and actual). Does nothing in Release builds.
+  void PrintOutputBufferSizes();
+#endif  // !defined(NDEBUG)
+
  protected:
   ~AudioManagerMac() override;
 
@@ -127,6 +133,22 @@ class MEDIA_EXPORT AudioManagerMac : public AudioManagerBase {
   // sample rate has changed, otherwise does nothing.
   void HandleDeviceChanges();
 
+  // Returns true if any active input stream is using the specified |device_id|.
+  bool AudioDeviceIsUsedForInput(AudioDeviceID device_id);
+
+  // This method is called when an output stream has been released and it takes
+  // the given |device_id| and scans all active output streams that are
+  // using this id. The goal is to find a new (larger) I/O buffer size which
+  // can be applied to all active output streams since doing so will save
+  // system resources.
+  // Note that, it is only called if no input stream is also using the device.
+  // Example: two active output streams where #1 wants 1024 as buffer size but
+  // is using 256 since stream #2 wants it. Now, if stream #2 is closed down,
+  // the native I/O buffer size will be increased to 1024 instead of 256.
+  // TODO(henrika): possibly extend the scheme to also take input streams into
+  // account.
+  bool IncreaseIOBufferSizeIfPossible(AudioDeviceID device_id);
+
   std::unique_ptr<AudioDeviceListenerMac> output_device_listener_;
 
   // Track the output sample-rate and the default output device