Update padding of file action buttons

This way the file list header height stays the same whether the action
buttons are displayed or hidden, and reduces unnecessary content
shifting.

Change-Id: Ie530c6ff797df3b24cd54e32b62fdf5e934f5c87
diff --git a/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.html b/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.html
index 4b158d3..7524abcb 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.html
+++ b/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.html
@@ -110,6 +110,11 @@
         align-items: center;
         display: flex;
       }
+      .fileViewActions gr-button {
+        --gr-button: {
+          padding: 2px 4px;
+        }
+      }
       .fileViewActions > *:not(:last-child) {
         margin-right: 5px;
       }