Revert "Merge pull request rails#5750 from ahoward/master"

This reverts commit 174cf8b, reversing
changes made to 7ecd6a7.
The reverted commit improved the performance in the wrong place, now we
have added this 6ddbd18 improvement.

actionpack/lib/action_dispatch/routing/url_for.rb

@@ -147,16 +147,7 @@ def url_for(options = nil)
         when nil
           _routes.url_for(url_options.symbolize_keys)
         when Hash
-          symbolized = {}
-          options.keys.each do |k|
-            sym = k.to_sym
-            symbolized[sym] = options[k] unless symbolized.has_key?(sym)
-          end
-          url_options.keys.each do |k|
-            sym = k.to_sym
-            symbolized[sym] = url_options[k] unless symbolized.has_key?(sym)
-          end
-          _routes.url_for(symbolized)
+          _routes.url_for(options.symbolize_keys.reverse_merge!(url_options))
         when String
           options
         else

actionpack/test/controller/url_for_test.rb

@@ -356,24 +356,6 @@ def test_with_hash_with_indifferent_access
         assert_equal("/c/a", W.new.url_for(HashWithIndifferentAccess.new('controller' => 'c', 'action' => 'a', 'only_path' => true)))
       end
 
-      def test_with_stringified_default_url_options
-        W.default_url_options['controller'] = 'd'
-        W.default_url_options['only_path']  = false
-        assert_equal("/c", W.new.url_for(:controller => 'c', :only_path => true))
-
-        W.default_url_options['action'] = 'b'
-        assert_equal("/c/a", W.new.url_for(:controller => 'c', :action => 'a', :only_path => true))
-      end
-
-      def test_with_stringified_default_url_options_and_without_options
-        W.default_url_options['controller'] = 'c'
-        W.default_url_options['only_path']  = true
-        assert_equal("/c", W.new.url_for)
-
-        W.default_url_options['action'] = 'a'
-        assert_equal("/c/a", W.new.url_for)
-      end
-
       def test_url_params_with_nil_to_param_are_not_in_url
         assert_equal("/c/a", W.new.url_for(:only_path => true, :controller => 'c', :action => 'a', :id => Struct.new(:to_param).new(nil)))
       end