ChangeScreen2: Use pointer cursor on message headers

The header is clickable. Use pointer cursor to denote this.

Change-Id: Ibbbeebab244fdd447504f310f0f48bd9b35ffaa8

gerrit-gwtui/src/main/java/com/google/gerrit/client/change/Message.ui.xml

@@ -30,6 +30,10 @@ limitations under the License.
       -webkit-border-bottom-right-radius: 8px;
     }
 
+    .header {
+      cursor: pointer;
+    }
+
     .avatar {
       position: absolute;
       width: 26px;
@@ -107,7 +111,7 @@ limitations under the License.
       addStyleNames='{style.closed}'>
     <c:AvatarImage ui:field='avatar' styleName='{style.avatar}'/>
     <div class='{style.contents}'>
-      <g:HTMLPanel ui:field='header'>
+      <g:HTMLPanel ui:field='header' styleName='{style.header}'>
         <div class='{style.name}' ui:field='name'/>
         <div ui:field='summary' class='{style.summary}'/>
         <div class='{style.date}' ui:field='date'/>