Add selected background to history groups

 Bug: 3370856

Change-Id: Iac6436279e1e3a5c91e2c9637b66bbcb74e3d265
diff --git a/res/layout/history_header.xml b/res/layout/history_header.xml
index e03b009..f77a697 100644
--- a/res/layout/history_header.xml
+++ b/res/layout/history_header.xml
@@ -21,4 +21,5 @@
         android:textAppearance="?android:attr/textAppearanceMedium"
         android:paddingLeft="35dip"
         android:gravity="center_vertical"
-        />
\ No newline at end of file
+        android:background="?android:attr/activatedBackgroundIndicator"
+        />