add 2x version of logo for sticky bar

Change-Id: I5127d308ee820d4e77798ebe4aaa0f385b797383
diff --git a/tools/droiddoc/templates-sdk/assets/css/default.css b/tools/droiddoc/templates-sdk/assets/css/default.css
index 522b237..688d048 100644
--- a/tools/droiddoc/templates-sdk/assets/css/default.css
+++ b/tools/droiddoc/templates-sdk/assets/css/default.css
@@ -4094,6 +4094,7 @@
   width: 26px;
   height: 25px;
   background: url(../images/dac_logo.png);
+  background-image: -webkit-image-set(url(../images/dac_logo.png) 1x, url(../images/dac_logo@2x.png) 2x);
   z-index: 52;
   position: relative;
 }