MDL-39871 Blocks,Themes: Swap block regions in RTL mode (using pre-defined array)

lib/outputlib.php

@@ -487,6 +487,11 @@ class theme_config {
             }
         }
 
+        // Use parent theme's "blockrtlmanipulations" if it was defined and if it was not defined on current theme.
+        if (empty($this->blockrtlmanipulations) and !empty($parent_config->blockrtlmanipulations)) {
+            $this->blockrtlmanipulations = $parent_config->blockrtlmanipulations;
+        }
+
         //fix arrows if needed
         $this->check_theme_arrows();
     }