Use display rather than visibility to remove closed expansion panel content from the flow.

Author: josephperrott

src/lib/expansion/expansion-animations.ts

@@ -53,8 +53,8 @@ export const matExpansionAnimations: {
 
   /** Animation that expands and collapses the panel content. */
   bodyExpansion: trigger('bodyExpansion', [
-    state('collapsed', style({height: '0px', visibility: 'hidden'})),
-    state('expanded', style({height: '*', visibility: 'visible'})),
+    state('collapsed', style({height: '0px', display: 'none'})),
+    state('expanded', style({height: '*', display: 'block'})),
     transition('expanded <=> collapsed', animate(EXPANSION_PANEL_ANIMATION_TIMING)),
   ])
 };