Schema for newly defined entity types is never created

@plach doesn't this mean that:

1. Install a module
2. Module adds an entity type in a new release
3. Update that module
4. Site is hosed without manual intervention

If so I think the upgrade path tag is right, but feel free to untag if this isn't the case.

1. +++ b/core/modules/locale/src/Tests/LocaleTranslatedSchemaDefinitionTest.php
   @@ -31,6 +31,8 @@ protected function setUp() {
        $this->config('system.site')->set('langcode', 'fr')->save();
   +    // Make sure new entity type definitions are processed.
   +    \Drupal::service('entity.definition_update_manager')->applyUpdates();
        // Clear all caches so that the base field definition, its cache in the
        // entity manager, the t() cache, etc. are all cleared.
   

   Why is this needed here?

2. +++ b/core/modules/system/tests/modules/entity_test/src/Entity/EntityTestNew.php
   @@ -0,0 +1,35 @@
   + *   label = @Translation("Test entity new"),
   + *   handlers = {
   + *     "storage_schema" = "Drupal\entity_test\EntityTestStorageSchema"
   + *   },
   + *   base_table = "entity_test_new",
   + *   fieldable = TRUE,
   + *   persistent_cache = FALSE,
   

   I think we don't need the custom handler and fieldable/cache definitions, to keep this as short as possible?

   Also, I think "New test entity" reads a bit better?

RTBC apart from those nitpicks I think.

Great, this looks good to me then.

This issue addresses a critical bug and is allowed per https://www.drupal.org/core/beta-changes. Committed 8007ab1 and pushed to 8.0.x. Thanks!