add placeholder for platform name in download button.
This change depends on the following change to the script that loads the platform name...
https://googleplex-android-review.git.corp.google.com/#/c/752776/

Change-Id: I7c9962f58d09d7a7f40dc6faa63014385b296498
(cherry picked from commit 3c2dc05e3da3fdf2d19bb8793c12411a46eb8d15)
diff --git a/docs/html/sdk/index.jd b/docs/html/sdk/index.jd
index dbc0f35..b57e6a7 100644
--- a/docs/html/sdk/index.jd
+++ b/docs/html/sdk/index.jd
@@ -289,7 +289,7 @@
 </ul>
 
 <a class="online landing-button green download-bundle-button"
-href="#Other" >Download Android Studio</a>
+href="#Other" >Download Android Studio<br/><span class='small'></span></a>
 
 <!-- this appears when viewing the offline docs -->
 <p class="offline">