Add entry for schema cache dump to CHANGELOG.md.

activerecord/CHANGELOG.md

@@ -1,5 +1,28 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Added the schema cache dump feature.
+
+    `Schema cache dump` feature was implemetend. This feature can dump/load internal state of `SchemaCache` instance
+    because we want to boot rails more quickly when we have many models.
+
+    Usage notes:
+
+      1) execute rake task.
+      RAILS_ENV=production bundle exec rake db:schema:cache:dump
+      => generate db/schema_cache.dump
+
+      2) add config.use_schema_cache_dump = true in config/production.rb. BTW, true is default.
+
+      3) boot rails.
+      RAILS_ENV=production bundle exec rails server
+      => use db/schema_cache.db
+
+      4) If you remove clear dumped cache, execute rake task.
+      RAILS_ENV=production bundle exec rake db:schema:cache:clear
+      => remove db/schema_cache.dump
+
+    *kennyj*
+
 *   Added support for partial indices to PostgreSQL adapter
 
     The `add_index` method now supports a `where` option that receives a