Move meta/meta_key handling inside adapter.

lib/active_model/serializer/adapter/base.rb

@@ -37,11 +37,11 @@ module ActiveModel
         private
 
         def meta
-          serializer.meta if serializer.respond_to?(:meta)
+          instance_options.fetch(:meta, nil)
         end
 
         def meta_key
-          serializer.meta_key || 'meta'.freeze
+          instance_options.fetch(:meta_key, 'meta'.freeze)
         end
 
         def root

lib/active_model/serializer/array_serializer.rb

@@ -5,7 +5,7 @@ module ActiveModel
       include Enumerable
       delegate :each, to: :@serializers
 
-      attr_reader :object, :root, :meta, :meta_key
+      attr_reader :object, :root
 
       def initialize(resources, options = {})
         @root = options[:root]
@@ -21,8 +21,6 @@ module ActiveModel
             serializer_class.new(resource, options.except(:serializer))
           end
         end
-        @meta     = options[:meta]
-        @meta_key = options[:meta_key]
       end
 
       def json_key