fix the 'to top' link; it wasn't appearing due to a previous CSS change

Change-Id: I00aa080982f5e5d90fd6abcf6e19d41d1727b444
diff --git a/tools/droiddoc/templates-sdk/assets/css/default.css b/tools/droiddoc/templates-sdk/assets/css/default.css
index 83d32d3..c3eb8bc 100644
--- a/tools/droiddoc/templates-sdk/assets/css/default.css
+++ b/tools/droiddoc/templates-sdk/assets/css/default.css
@@ -2263,12 +2263,16 @@
 
 
 /* nav tree */
-#side-nav, #devdoc-nav, #swapper,
+#side-nav, #swapper,
 #nav-tree, #tree-list {
   overflow:hidden;
   margin-left:0;
 }
 
+#devdoc-nav {
+  overflow:visible !important; /* To keep the "to top" button visible */
+}
+
 #nav-tree ul {
   list-style:none;
   padding:0;