USAGE_ASSISTANT/ACCESSIBILITY in audio policy manager

Add support for USAGE_ASSISTANT.
Fix stream type for USAGE_ACCESSIBILITY.

Test: enable Talkback, check volume; make
Bug: 30947943

Change-Id: Ie35adf0115dce1fac6d3deddc1e57e36b36913f6
diff --git a/services/audiopolicy/managerdefault/AudioPolicyManager.cpp b/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
index 2f4cc1d..43c1b0a 100644
--- a/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
+++ b/services/audiopolicy/managerdefault/AudioPolicyManager.cpp
@@ -5336,6 +5336,7 @@
     switch (attr->usage) {
     case AUDIO_USAGE_MEDIA:
     case AUDIO_USAGE_GAME:
+    case AUDIO_USAGE_ASSISTANT:
     case AUDIO_USAGE_ASSISTANCE_NAVIGATION_GUIDANCE:
         return AUDIO_STREAM_MUSIC;
     case AUDIO_USAGE_ASSISTANCE_ACCESSIBILITY:
@@ -5391,6 +5392,7 @@
     case AUDIO_USAGE_ASSISTANCE_SONIFICATION:
     case AUDIO_USAGE_GAME:
     case AUDIO_USAGE_VIRTUAL_SOURCE:
+    case AUDIO_USAGE_ASSISTANT:
         break;
     default:
         return false;