audio: add 'useForVolume' field to 'gain'.

BUG: 144081761
Test: xmllint --noout --xinclude --schema \
      hardware/interfaces/audio/5.0/config/audio_policy_configuration.xsd \
      frameworks/av/services/audiopolicy/config/audio_policy_configuration*.xml
      xmllint --noout --schema \
      hardware/interfaces/audio/5.0/config/audio_policy_configuration.xsd \
      --xinclude out/target/product/*/vendor/etc/audio_policy_configuration.xml

Change-Id: I0ee9114f750186b479a2ebee5dfcd946d9ef3196
diff --git a/audio/5.0/config/api/current.txt b/audio/5.0/config/api/current.txt
index c665781..a1d8e1e 100644
--- a/audio/5.0/config/api/current.txt
+++ b/audio/5.0/config/api/current.txt
@@ -237,6 +237,7 @@
     method public audio.policy.configuration.V5_0.GainMode getMode();
     method public String getName();
     method public int getStepValueMB();
+    method public boolean getUseForVolume();
     method public void setChannel_mask(String);
     method public void setDefaultValueMB(int);
     method public void setMaxRampMs(int);
@@ -246,6 +247,7 @@
     method public void setMode(audio.policy.configuration.V5_0.GainMode);
     method public void setName(String);
     method public void setStepValueMB(int);
+    method public void setUseForVolume(boolean);
   }
 
   public class GlobalConfiguration {