Schematize vold system properties

Properties accessed across partitions are now schematized and will
become APIs to make explicit interfaces among partitions.

Bug: 117924132
Test: m -j
Change-Id: Id2a696c621015d46015d5de0e7aef987e9e01b54
(cherry picked from commit 64af0081cc1a8babe19b0552122e35211fc84c9d)

src/com/android/settings/MasterClear.java

@@ -39,6 +39,7 @@ import android.os.SystemProperties;
 import android.os.UserHandle;
 import android.os.UserManager;
 import android.provider.Settings;
+import android.sysprop.VoldProperties;
 import android.telephony.euicc.EuiccManager;
 import android.text.TextUtils;
 import android.util.Log;
@@ -440,7 +441,7 @@ public class MasterClear extends InstrumentedFragment implements OnGlobalLayoutL
     }
 
     private boolean isExtStorageEncrypted() {
-        String state = SystemProperties.get("vold.decrypt");
+        String state = VoldProperties.decrypt().orElse("");
         return !"".equals(state);
     }