Change the expand button to unfold-more.

This isn't awesome, but it was the best icon I could find and it
at least will be more clear since it's not using something that's
overloaded for opening menus.

BUG=404049
NOTRY=true

Review URL: https://codereview.chromium.org/475323002

git-svn-id: svn://svn.chromium.org/blink/trunk@180393 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Tools/GardeningServer/ui/ct-test-list.html

@@ -47,7 +47,7 @@ found in the LICENSE file.
         <template if="{{ group.name && group.tests.length > 1 && !group.expanded }}">
           <div>
             {{ groups.step }} {{ group.name }} ({{ group.tests.length }} Tests)
-            <paper-icon-button id="expand" icon="more-vert" step="{{ groups.step }}" group="{{ group.name }}" on-click="{{ _expand }}"></paper-icon-button>
+            <paper-icon-button id="expand" icon="unfold-more" step="{{ groups.step }}" group="{{ group.name }}" on-click="{{ _expand }}"></paper-icon-button>
           </div>
         </template>
       </template>