s/Dropdown/Drop Down

Author: frankiefu

demo.html

@@ -78,7 +78,7 @@
 
       <core-item label="Menu Button" tag="paper-menu-button" url="../paper-menu-button/demo.html"></core-item>
 
-      <core-item label="Dropdown" tag="paper-dropdown" url="../paper-dropdown/demo.html"></core-item>
+      <core-item label="Drop Down" tag="paper-dropdown" url="../paper-dropdown/demo.html"></core-item>
 
       <core-item label="Item" tag="paper-item" url="../paper-item/demo.html"></core-item>