Bug 982495 - Add missing "break" in test_coalescence.html. r=surkov

accessible/tests/mochitest/events/test_coalescence.html

@@ -92,6 +92,7 @@
 
           case kShowElm:
             aNode.style.display = "block";
+            break;
 
           default:
             return INVOKER_ACTION_FAILED;