add the 'reference only' header design as a condition to the normal templates.

also add override for implementation to the to-root link path.
bug: 27667787

Change-Id: I79892ddb7c5053d5325afcd50016c726b34e1361

tools/droiddoc/templates-sdk/macros_override.cs

@@ -33,4 +33,12 @@
       <?cs set:count = count + #1 ?>
     <?cs /each ?>
   </table>
-<?cs /def ?>
+<?cs /def ?>
+
+<?cs def:doc_root_override() ?><?cs
+  if:referenceonly
+    ?>https://developer.android.com/<?cs
+  else ?><?cs
+    var:toroot ?><?cs
+  /if ?><?cs
+/def ?>