Entity translation and revision loosing meta for translation

Another maybe related bug:

1. Consider the previous scenario
2. Revert the revision where both languages had custom meta while current language is french

Bug: another revision is created, but the english version has the french custom meta

Patch solving the first problem. Just state your mind, don't commit, I've still some performance improvements to do.

Also if you could explain this part (line 426):

  // Ensure the data saves during node_save().
  if (isset($metatags[$langcode])) {
    // There are certain occasions when the old data and the new data are
    // *both* added to the $metatags array, in this case throw away the language
    // data.
    $lang_data = $metatags[$langcode];
    unset($metatags[$langcode]);
    if (empty($metatags)) {
      $metatags = $lang_data;
    }
  }

That's actually what's causing the second bug (but in the same function)

And here is another one, with performance fix and trying to mitigate "these certain occasions"

+++ b/metatag.module
@@ -442,6 +444,37 @@ function metatag_metatags_save($entity_type, $entity_id, $revision_id, $metatags
+            'language'    => $lang->language,

Typo here