audio policy: fix build with USE_LEGACY_AUDIO_POLICY

Bug: 17894512.
Change-Id: I6431c0b03ba02cf561413c34848a334caa0261fa
diff --git a/services/audiopolicy/AudioPolicyInterfaceImplLegacy.cpp b/services/audiopolicy/AudioPolicyInterfaceImplLegacy.cpp
index 9f66fd1..e1e81e1 100644
--- a/services/audiopolicy/AudioPolicyInterfaceImplLegacy.cpp
+++ b/services/audiopolicy/AudioPolicyInterfaceImplLegacy.cpp
@@ -24,6 +24,7 @@
 #include <system/audio.h>
 #include <system/audio_policy.h>
 #include <hardware/audio_policy.h>
+#include <media/AudioPolicyHelper.h>
 
 namespace android {
 
@@ -525,7 +526,7 @@
     return INVALID_OPERATION;
 }
 
-audio_io_handle_t AudioPolicyService::getOutputForAttr(const audio_attributes_t *attr __unused,
+audio_io_handle_t AudioPolicyService::getOutputForAttr(const audio_attributes_t *attr,
                                     uint32_t samplingRate,
                                     audio_format_t format,
                                     audio_channel_mask_t channelMask,