Correct expectations for pointerevents after slot changes.

These 3 points were missed previously:
- The mouse pointer moves off from the `shadow_host` to click `done`.
- After `slot` removal, the `slotted_child` remains un-rendered and
  also doesn't appear in the `parent.children` list.  So the
  `slotted_child` is effectively disconnected therefore not expected
  to receive any following event.  Firefox behaves this way too.
- The down/up events at `parent` are also dispatched to `shadow_root`.
  Both Chrome and Firefox behaves this way, matching the spec [1].

Manual test link: https://codepen.io/mustaqahmed/full/BaeRvdZ
[1] https://dom.spec.whatwg.org/#dispatching-events Steps 5.13 and 5.14.

Bug: 40156858
Change-Id: I7d9f50c7732b0dc81887dce86a323685b46fab17
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5640796
Reviewed-by: Robert Flack <[email protected]>
Commit-Queue: Mustaq Ahmed <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1317590}

Author: mustaqahmed

pointerevents/pointerevent_after_target_removed_from_slot.html

@@ -142,10 +142,10 @@
       "pointerover@child",
       "pointerenter@host", "pointerenter@parent", "pointerenter@slot", "pointerenter@child",
       "pointerdown@child", "(child-removed)",
-      "pointerout@child", "pointerleave@child",
-      "pointerover@parent", "pointerup@parent",
-      "pointerdown@parent", "pointerup@parent",
-      "pointerout@parent", "pointerleave@parent"
+      "pointerover@parent", "pointerup@parent", "pointerup@host",
+      "pointerdown@parent", "pointerdown@host", "pointerup@parent", "pointerup@host",
+      "pointerout@parent",
+      "pointerleave@parent", "pointerleave@host"
     ]
   );
   addPromiseTest(
@@ -155,9 +155,10 @@
       "pointerover@child",
       "pointerenter@host", "pointerenter@parent", "pointerenter@slot", "pointerenter@child",
       "pointerdown@child", "(child-removed)",
-      "pointerleave@slot", "pointerover@parent", "pointerup@parent",
-      "pointerdown@parent", "pointerup@parent",
-      "pointerout@parent", "pointerleave@parent"
+      "pointerleave@slot", "pointerover@parent", "pointerup@parent", "pointerup@host",
+      "pointerdown@parent", "pointerdown@host", "pointerup@parent", "pointerup@host",
+      "pointerout@parent",
+      "pointerleave@parent", "pointerleave@host"
     ]
   );
   addPromiseTest(
@@ -167,9 +168,10 @@
       "pointerover@child",
       "pointerenter@host", "pointerenter@parent", "pointerenter@slot", "pointerenter@child",
       "pointerdown@child", "pointerup@child", "(child-removed)",
-      "pointerout@child", "pointerleave@child",
-      "pointerover@parent", "pointerdown@parent", "pointerup@parent",
-      "pointerout@parent", "pointerleave@parent"
+      "pointerover@parent",
+      "pointerdown@parent", "pointerdown@host", "pointerup@parent", "pointerup@host",
+      "pointerout@parent",
+      "pointerleave@parent", "pointerleave@host"
     ]
   );
   addPromiseTest(
@@ -179,8 +181,10 @@
       "pointerover@child",
       "pointerenter@host", "pointerenter@parent", "pointerenter@slot", "pointerenter@child",
       "pointerdown@child", "pointerup@child", "(child-removed)",
-      "pointerleave@slot", "pointerover@parent", "pointerdown@parent", "pointerup@parent",
-      "pointerout@parent", "pointerleave@parent"
+      "pointerleave@slot", "pointerover@parent",
+      "pointerdown@parent", "pointerdown@host", "pointerup@parent", "pointerup@host",
+      "pointerout@parent",
+      "pointerleave@parent", "pointerleave@host"
     ]
   );
 </script>