Tool execution micro optimization...

... Don't create an extra list to reverse, just iterate over in reversed order.

lib/galaxy/tools/actions/__init__.py

@@ -178,9 +178,7 @@ def execute(self, tool, trans, incoming={}, return_job=False, set_output_hid=Tru
         input_names = []
         input_ext = 'data'
         input_dbkey = incoming.get( "dbkey", "?" )
-        inp_items = inp_data.items()
-        inp_items.reverse()
-        for name, data in inp_items:
+        for name, data in reversed(inp_data.items()):
             if not data:
                 data = NoneDataset( datatypes_registry=trans.app.datatypes_registry )
                 continue