Support scanDirectories with JNI callback function

MtpServer needs this function to update the database for directory
copy operation.

Test: Call this function from MtpServer and database is updated in
directory copy scenario.

Change-Id: I9b316f4dbf7f35922292c33ab02f9efebc867aa8
Signed-off-by: kyle_tso <kyle_tso@htc.com>

media/java/android/mtp/MtpDatabase.java

@@ -421,6 +421,12 @@ public class MtpDatabase implements AutoCloseable {
         }
     }
 
+    private void doScanDirectory(String path) {
+        String[] scanPath;
+        scanPath = new String[] { path };
+        mMediaScanner.scanDirectories(scanPath);
+    }
+
     private Cursor createObjectQuery(int storageID, int format, int parent) throws RemoteException {
         String where;
         String[] whereArgs;