Deprecate ActiveRecord#Base.default_scopes?

See #10107.

activerecord/CHANGELOG.md

 ## Rails 4.0.0 (unreleased) ##
 
+*   `#default_scopes?` is deprecated. Instead, do something like
+    `Post.default_scopes.empty?`.
+
+    *Agis Anastasopoulos*
+
 *   Default values for PostgreSQL bigint types now get parsed and dumped to the
     schema correctly.
 

activerecord/lib/active_record/scoping/default.rb

@@ -5,8 +5,17 @@ module Default
 
       included do
         # Stores the default scope for the class.
-        class_attribute :default_scopes, instance_writer: false
+        class_attribute :default_scopes, instance_writer: false, instance_predicate: false
+
         self.default_scopes = []
+
+        def self.default_scopes?
+          ActiveSupport::Deprecation.warn(
+            "#default_scopes? is deprecated. Do something like #default_scopes.empty? instead."
+          )
+
+          !!self.default_scopes
+        end
       end
 
       module ClassMethods