audio: fix stream type for accessibility usage

Make sure that accessibility prompts are heard when
a ringtone is active by forcing stream type
to AUDIO_STREAM_RING when phone state is AUDIO_MODE_RINGTONE.

Bug: 17558149.
Change-Id: Ia3bead8052fca5cbf282c267f7b9b06014fef628
diff --git a/services/audiopolicy/AudioPolicyService.h b/services/audiopolicy/AudioPolicyService.h
index 0044e7a..2cea40b 100644
--- a/services/audiopolicy/AudioPolicyService.h
+++ b/services/audiopolicy/AudioPolicyService.h
@@ -174,6 +174,8 @@
 
     virtual status_t releaseSoundTriggerSession(audio_session_t session);
 
+    virtual audio_mode_t getPhoneState();
+
             status_t doStopOutput(audio_io_handle_t output,
                                   audio_stream_type_t stream,
                                   int session = 0);
@@ -493,6 +495,7 @@
 
     // Manage all effects configured in audio_effects.conf
     sp<AudioPolicyEffects> mAudioPolicyEffects;
+    audio_mode_t mPhoneState;
 };
 
 }; // namespace android