AudioPolicy: callback for recording configuration change

Each AudioSession tracks start / end of recording, and sends
  a callback to AudioSystem.
AudioSystem tracks a single recording callback tracking
  input source and audio session number.

Change-Id: Ic065751d9ba013e03f2a6ad8dde02542e5465ec0
diff --git a/include/media/AudioPolicy.h b/include/media/AudioPolicy.h
index feed402..ff07b08 100644
--- a/include/media/AudioPolicy.h
+++ b/include/media/AudioPolicy.h
@@ -91,6 +91,12 @@
     uint32_t        mCbFlags; // flags indicating which callbacks to use, see kCbFlag*
 };
 
+
+// definitions for audio recording configuration updates
+// which update type is reported
+#define RECORD_CONFIG_EVENT_START 1
+#define RECORD_CONFIG_EVENT_STOP  0
+
 }; // namespace android
 
 #endif  // ANDROID_AUDIO_POLICY_H