Fix toggle icon in reference to match site-wide behavior.

Change-Id: I0743cd456210921c50777a37e2cf4580f79be64d
diff --git a/tools/droiddoc/templates-sdk-dev/assets/css/default.css b/tools/droiddoc/templates-sdk-dev/assets/css/default.css
index 14e3be7..f150a73 100644
--- a/tools/droiddoc/templates-sdk-dev/assets/css/default.css
+++ b/tools/droiddoc/templates-sdk-dev/assets/css/default.css
@@ -7419,7 +7419,7 @@
 }
 
 .dac-reference-nav-toggle::before {
-  background: transparent url(../images/styles/disclosure_down.png) no-repeat center center;
+  background: transparent url(../images/styles/disclosure_up.png) no-repeat center center;
   content: '';
   display: block;
   height: 19px;