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/media/libmedia/AudioSystem.cpp b/media/libmedia/AudioSystem.cpp
index 8db72ee..d1aeba1 100644
--- a/media/libmedia/AudioSystem.cpp
+++ b/media/libmedia/AudioSystem.cpp
@@ -1033,6 +1033,12 @@
     }
 }
 
+void AudioSystem::AudioPolicyServiceClient::onDynamicPolicyMixStateUpdate(
+        String8 regId, int32_t state)
+{
+    ALOGV("TODO propagate onDynamicPolicyMixStateUpdate(%s, %d)", regId.string(), state);
+}
+
 void AudioSystem::AudioPolicyServiceClient::binderDied(const wp<IBinder>& who __unused)
 {
     {