fix(material/menu): clicks on disabled item closing the menu

Adds an overlay on top of the content of a disabled menu item in order to capture clicks and prevent the menu from closing when clicking on it.

Fixes #19173.

Author: crisbeto

src/material-experimental/mdc-menu/menu.scss

@@ -67,17 +67,25 @@ mat-menu {
   min-height: map.get($height-config, default);
 
   &[disabled] {
-    // Usually every click inside the menu closes it, however some browsers will stop events
-    // when the user clicks on a disabled item, **except** when the user clicks on a non-disabled
-    // child node of the disabled button. This is inconsistent because some regions of a disabled
-    // button will still cause the menu to close and some won't (see #16694). We make the behavior
-    // more consistent by disabling pointer events and allowing the user to click through.
-    pointer-events: none;
     cursor: default;
 
     // This is the same as `mdc-list-mixins.list-disabled-opacity` which
     // we can't use directly, because it comes with some selectors.
     opacity: mdc-list-variables.$content-disabled-opacity;
+
+    // The browser prevents clicks on disabled buttons from propagating which prevents the menu
+    // from closing, but clicks on child nodes still propagate which is inconsistent (see #16694).
+    // In order to keep the behavior consistent and prevent the menu from closing, we add an overlay
+    // on top of the content that will catch all the clicks while disabled.
+    &::before {
+      display: block;
+      position: absolute;
+      content: '';
+      top: 0;
+      left: 0;
+      bottom: 0;
+      right: 0;
+    }
   }
 
   .mat-icon {

src/material/menu/menu.scss

@@ -53,13 +53,18 @@ mat-menu {
   @include menu-common.item-base();
   position: relative;
 
-  &[disabled] {
-    // Usually every click inside the menu closes it, however some browsers will stop events
-    // when the user clicks on a disabled item, **except** when the user clicks on a non-disabled
-    // child node of the disabled button. This is inconsistent because some regions of a disabled
-    // button will still cause the menu to close and some won't (see #16694). We make the behavior
-    // more consistent by disabling pointer events and allowing the user to click through.
-    pointer-events: none;
+  // The browser prevents clicks on disabled buttons from propagating which prevents the menu
+  // from closing, but clicks on child nodes still propagate which is inconsistent (see #16694).
+  // In order to keep the behavior consistent and prevent the menu from closing, we add an overlay
+  // on top of the content that will catch all the clicks while disabled.
+  &[disabled]::before {
+    display: block;
+    position: absolute;
+    content: '';
+    top: 0;
+    left: 0;
+    bottom: 0;
+    right: 0;
   }
 
   @include a11y.high-contrast(active, off) {