leave the padding on the backupkeys

this was self-consistent on the device, but the host tool
treats lack of padding in a different way.

Bug:10778984
Change-Id: I47f653a98f23ff0ce54218d100e0c8e2f92b67fa

src/com/android/launcher3/LauncherBackupAgent.java

@@ -644,7 +644,7 @@ public class LauncherBackupAgent extends BackupAgent {
 
     /** keys need to be strings, serialize and encode. */
     private String keyToBackupKey(Key key) {
-        return Base64.encodeToString(Key.toByteArray(key), Base64.NO_WRAP | Base64.NO_PADDING);
+        return Base64.encodeToString(Key.toByteArray(key), Base64.NO_WRAP);
     }
 
     /** keys need to be strings, decode and parse. */

util/com/android/launcher3/DecoderRing.java

@@ -100,7 +100,7 @@ class DecoderRing {
         if (type == Key.class) {
             Key key = new Key();
             try {
-                MessageNano.mergeFrom(key, byteStream.toByteArray());
+                key = Key.parseFrom(byteStream.toByteArray());
             } catch (InvalidProtocolBufferNanoException e) {
                 System.err.println("failed to parse proto: " + e);
                 System.exit(1);