Cache partial variable names to reduce garbage

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8793 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_view/partials.rb

@@ -172,7 +172,9 @@ def partial_counter_name(partial_name)
       end
 
       def partial_variable_name(partial_name)
-        partial_name.split('/').last.split('.').first.intern
+        @@partial_variable_names ||= {}
+        @@partial_variable_names[partial_name] ||=
+          partial_name.split('/').last.split('.').first.intern
       end
 
       def extracting_object(partial_name, object_assigns)