Fix spacing between change status chip and change number when logged out

On the change screen the header section shows the star icon between the
change status chip and the change number. If the user is not logged in
the star icon is hidden, which makes the change number appear right next
to the change status chip, without any spacing. To preserve the space
that is used by the star icon use 'visibility: hidden' to hide it rather
than 'display: none'. 'visibility: hidden' hides an element but leaves
space where it would have been.

Bug: Issue 12268
Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: I2bad7075cc1d310167cf5a93954f649c5313e88e
diff --git a/polygerrit-ui/app/elements/shared/gr-change-star/gr-change-star_html.ts b/polygerrit-ui/app/elements/shared/gr-change-star/gr-change-star_html.ts
index 6c0f6f7..d404795 100644
--- a/polygerrit-ui/app/elements/shared/gr-change-star/gr-change-star_html.ts
+++ b/polygerrit-ui/app/elements/shared/gr-change-star/gr-change-star_html.ts
@@ -36,6 +36,10 @@
         var(--line-height-normal, 20px)
       );
     }
+    :host([hidden]) {
+      visibility: hidden;
+      display: block !important;
+    }
   </style>
   <button
     role="checkbox"