Add system prop to track if oem unlock is allowed

This state is never trusted, but it permits us to build
more appropriately message the user if their device is in
a state where its OK to reset.

Change-Id: I26cc0f928d7fdeff8837e4c2c4b8859fede7846d

services/core/java/com/android/server/PersistentDataBlockService.java

@@ -70,6 +70,7 @@ public class PersistentDataBlockService extends SystemService {
     // Limit to 100k as blocks larger than this might cause strain on Binder.
     private static final int MAX_DATA_BLOCK_SIZE = 1024 * 100;
     public static final int DIGEST_SIZE_BYTES = 32;
+    private static final String OEM_UNLOCK_PROP = "sys.oem_unlock_allowed";
 
     private final Context mContext;
     private final String mDataBlockFile;
@@ -108,12 +109,15 @@ public class PersistentDataBlockService extends SystemService {
     }
 
     private void formatIfOemUnlockEnabled() {
-        if (doGetOemUnlockEnabled()) {
+        boolean enabled = doGetOemUnlockEnabled();
+        if (enabled) {
             synchronized (mLock) {
                 formatPartitionLocked();
                 doSetOemUnlockEnabledLocked(true);
             }
         }
+
+        SystemProperties.set(OEM_UNLOCK_PROP, enabled ? "1" : "0");
     }
 
     private void enforceOemUnlockPermission() {
@@ -133,7 +137,6 @@ public class PersistentDataBlockService extends SystemService {
             throw new SecurityException("Only the Owner is allowed to change OEM unlock state");
         }
     }
-
     private int getTotalDataSizeLocked(DataInputStream inputStream) throws IOException {
         // skip over checksum
         inputStream.skipBytes(DIGEST_SIZE_BYTES);
@@ -291,6 +294,7 @@ public class PersistentDataBlockService extends SystemService {
             Slog.e(TAG, "unable to access persistent partition", e);
             return;
         } finally {
+            SystemProperties.set(OEM_UNLOCK_PROP, enabled ? "1" : "0");
             IoUtils.closeQuietly(outputStream);
         }
     }