AudioPolicyManager: notification of dynamic policy mix activity

Implement non-stream type specific ref counting in output
  descriptors to keep track of mix activity.
Notify audio policy client of mix activity changes.

Bug 20226914

Change-Id: Iec939cb640c58056f88947b611d23b4bb6d8a11b
diff --git a/include/media/IAudioPolicyServiceClient.h b/include/media/IAudioPolicyServiceClient.h
index 59df046..a7f2cc3 100644
--- a/include/media/IAudioPolicyServiceClient.h
+++ b/include/media/IAudioPolicyServiceClient.h
@@ -35,6 +35,8 @@
     virtual void onAudioPortListUpdate() = 0;
     // Notifies a change of audio patch configuration.
     virtual void onAudioPatchListUpdate() = 0;
+    // Notifies a change in the mixing state of a specific mix in a dynamic audio policy
+    virtual void onDynamicPolicyMixStateUpdate(String8 regId, int32_t state) = 0;
 };