don't hold a reference to env in the options object

I want to decouple Rails from the rack ENV as much as possible.  We
should try to keep as few references to the env as possible

actionpack/lib/action_dispatch/request/session.rb

@@ -17,7 +17,7 @@ module ActionDispatch
         session.merge! session_was if session_was
 
         set(env, session)
-        Options.set(env, Request::Session::Options.new(store, env, default_options))
+        Options.set(env, Request::Session::Options.new(store, default_options))
         session
       end
 
@@ -38,20 +38,19 @@ module ActionDispatch
           env[ENV_SESSION_OPTIONS_KEY]
         end
 
-        def initialize(by, env, default_options)
+        def initialize(by, default_options)
           @by       = by
-          @env      = env
           @delegate = default_options.dup
         end
 
         def [](key)
-          if key == :id
-            @delegate.fetch(key) {
-              @delegate[:id] = @by.send(:extract_session_id, @env)
-            }
-          else
-            @delegate[key]
-          end
+          @delegate[key]
+        end
+
+        def id(env)
+          @delegate.fetch(:id) {
+            @by.send(:extract_session_id, env)
+          }
         end
 
         def []=(k,v);         @delegate[k] = v; end
@@ -68,7 +67,7 @@ module ActionDispatch
       end
 
       def id
-        options[:id]
+        options.id(@env)
       end
 
       def options
@@ -78,8 +77,7 @@ module ActionDispatch
       def destroy
         clear
         options = self.options || {}
-        new_sid = @by.send(:destroy_session, @env, options[:id], options)
-        options[:id] = new_sid # Reset session id with a new value or nil
+        @by.send(:destroy_session, @env, options.id(@env), options)
 
         # Load the new sid to be written with the response
         @loaded = false