Bug 1489269 [wpt PR 12879] - HTML: Add test for document.open() and M…

…utationObserver, a=testonly

Automatic update from web-platform-testsHTML: Add test for document.open() and MutationObserver (#12879)

For whatwg/html#3818.
--

wpt-commits: cf0ea11ebe5801798d0390f7747b056110f74ed9
wpt-pr: 12879

testing/web-platform/meta/MANIFEST.json

@@ -368902,6 +368902,12 @@
      {}
     ]
    ],
+   "html/webappapis/dynamic-markup-insertion/opening-the-input-stream/mutation-observer.window.js": [
+    [
+     "/html/webappapis/dynamic-markup-insertion/opening-the-input-stream/mutation-observer.window.html",
+     {}
+    ]
+   ],
    "html/webappapis/dynamic-markup-insertion/opening-the-input-stream/no-new-global.window.js": [
     [
      "/html/webappapis/dynamic-markup-insertion/opening-the-input-stream/no-new-global.window.html",
@@ -613663,6 +613669,10 @@
    "4efbb863c6372a3ee04d11f38d7ee56a44a2ac7d",
    "testharness"
   ],
+  "html/webappapis/dynamic-markup-insertion/opening-the-input-stream/mutation-observer.window.js": [
+   "34e73146a9d8e4ecab1e74a0079cd721e7306e59",
+   "testharness"
+  ],
   "html/webappapis/dynamic-markup-insertion/opening-the-input-stream/no-new-global.window.js": [
    "d4a9296fca66d3017c267a8d8951bef2dcbee238",
    "testharness"

testing/web-platform/tests/html/webappapis/dynamic-markup-insertion/opening-the-input-stream/mutation-observer.window.js

@@ -0,0 +1,19 @@
+async_test(t => {
+  const frame = document.body.appendChild(document.createElement("iframe"));
+  t.add_cleanup(() => { frame.remove(); });
+  const originalHTMLElement = frame.contentDocument.documentElement;
+  assert_equals(originalHTMLElement.localName, "html");
+  const observer = new frame.contentWindow.MutationObserver(t.step_func_done(records => {
+    // Even though we passed `subtree: true` to observer.observe, due to the
+    // fact that "replace all" algorithm removes children with the "suppress
+    // observers flag" set, we still only get the html element as the sole
+    // removed node.
+    assert_equals(records.length, 1);
+    assert_equals(records[0].type, "childList");
+    assert_equals(records[0].target, frame.contentDocument);
+    assert_array_equals(records[0].addedNodes, []);
+    assert_array_equals(records[0].removedNodes, [originalHTMLElement]);
+  }));
+  observer.observe(frame.contentDocument, { childList: true, subtree: true });
+  assert_equals(frame.contentDocument.open(), frame.contentDocument);
+}, "document.open() should inform mutation observer of node removal");