ChangeScreen2: Add one line padding below History

This prevents the "Press ? to view keyboard shortcuts" from being
right up against the last message.

Change-Id: I550ff3f942a5965231e850be0ad9d6123eb6648d
(cherry picked from commit c737d282fa51f9d2cf8a451623c6a536c98feaec)
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/ChangeScreen2.ui.xml b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/ChangeScreen2.ui.xml
index 9f9bdce..49883ee 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/ChangeScreen2.ui.xml
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/ChangeScreen2.ui.xml
@@ -29,6 +29,10 @@
     @def INFO_WIDTH 450px;
     @def HEADER_HEIGHT 29px;
 
+    .cs2 {
+      margin-bottom: 1em;
+    }
+
     .headerLine {
       position: relative;
       background-color: trimColor;
@@ -258,7 +262,7 @@
     }
   </ui:style>
 
-  <g:HTMLPanel>
+  <g:HTMLPanel styleName='{style.cs2}'>
     <g:HTMLPanel styleName='{style.headerLine}' ui:field='headerLine'>
       <div class='{style.idBlock}'>
         <c:StarIcon ui:field='star' styleName='{style.star}'/>