message: Clarify the code to create a newKeyId.
  I found the previous code hard to understand, since I didn't know to where the "continue" statement jumps: there's a for and a while loop. I don't think there's a bug, but I think the new code is much easier to understand anyhow.
diff: @@ -243,16 +243,20 @@ public final class KeysetManager {
  }
  @GuardedBy("this")
  - private synchronized int newKeyId() {
  - int keyId = randPositiveInt();
  - while (true) {
  + private synchronized boolean keyIdExists(int keyId) {
  for (Keyset.Key key : keysetBuilder.getKeyList()) {
  if (key.getKeyId() == keyId) {
  - keyId = randPositiveInt();
  - continue;
  + return true;
  }
  }
  - break;
  + return false;
  + }
  +
  + @GuardedBy("this")
  + private synchronized int newKeyId() {
  + int keyId = randPositiveInt();
  + while (keyIdExists(keyId)) {
  + keyId = randPositiveInt();
  }
  return keyId;
  }
  