HTML: document.open() and document's URL (#12636)

For whatwg/html#3946.

Adapts the basic test in
#10817 for a number of
advanced scenarios regarding document activity.

Co-authored-by: Anne van Kesteren <annevk@annevk.nl>

html/webappapis/dynamic-markup-insertion/opening-the-input-stream/url.window.js

@@ -0,0 +1,87 @@
+test(t => {
+  const frame = document.body.appendChild(document.createElement("iframe"));
+  t.add_cleanup(() => frame.remove());
+  assert_equals(frame.contentDocument.URL, "about:blank");
+  assert_equals(frame.contentWindow.location.href, "about:blank");
+  frame.contentDocument.open();
+  assert_equals(frame.contentDocument.URL, document.URL);
+  assert_equals(frame.contentWindow.location.href, document.URL);
+}, "document.open() changes document's URL (fully active document)");
+
+async_test(t => {
+  const blankURL = new URL("/common/blank.html", document.URL).href;
+  const frameURL = new URL("resources/page-with-frame.html", document.URL).href;
+  const frame = document.body.appendChild(document.createElement("iframe"));
+  t.add_cleanup(() => frame.remove());
+  frame.onload = t.step_func(() => {
+    assert_equals(frame.contentDocument.URL, frameURL);
+    assert_equals(frame.contentWindow.location.href, frameURL);
+    const childFrame = frame.contentDocument.querySelector("iframe");
+    const childDoc = childFrame.contentDocument;
+    const childWin = childFrame.contentWindow;
+    assert_equals(childDoc.URL, blankURL);
+    assert_equals(childWin.location.href, blankURL);
+
+    // Right now childDoc is still fully active.
+
+    frame.onload = t.step_func_done(() => {
+      // Now childDoc is still active but no longer fully active.
+      childDoc.open();
+      assert_equals(childDoc.URL, blankURL);
+      assert_equals(childWin.location.href, blankURL);
+    });
+    frame.src = "/common/blank.html";
+  });
+  frame.src = frameURL;
+}, "document.open() does not change document's URL (active but not fully active document)");
+
+test(t => {
+  const frame = document.body.appendChild(document.createElement("iframe"));
+  t.add_cleanup(() => frame.remove());
+  const doc = frame.contentDocument;
+
+  // Right now the frame is connected and it has an active document.
+  assert_equals(doc.URL, "about:blank");
+
+  frame.remove();
+
+  // Now the frame is no longer connected. Its document is no longer active.
+  assert_equals(doc.URL, "about:blank");
+  assert_equals(doc.open(), doc);
+  assert_equals(doc.URL, "about:blank");
+}, "document.open() does not change document's URL (non-active document with an associated Window object; frame is removed)");
+
+async_test(t => {
+  const frame = document.createElement("iframe");
+  t.add_cleanup(() => frame.remove());
+
+  frame.onload = t.step_func(() => {
+    const doc = frame.contentDocument;
+    // Right now the frame is connected and it has an active document.
+    assert_equals(doc.URL, "about:blank");
+
+    frame.onload = t.step_func_done(() => {
+      // Now even though the frame is still connected, its document is no
+      // longer active.
+      assert_not_equals(frame.contentDocument, doc);
+      assert_equals(doc.URL, "about:blank");
+      assert_equals(doc.open(), doc);
+      assert_equals(doc.URL, "about:blank");
+    });
+
+    frame.src = "/common/blank.html";
+  });
+
+  // We need to connect the frame after the load event is set up to mitigate
+  // against https://crbug.com/569511.
+  document.body.appendChild(frame);
+}, "document.open() does not change document's URL (non-active document with an associated Window object; navigated away)");
+
+test(t => {
+  const frame = document.body.appendChild(document.createElement("iframe"));
+  t.add_cleanup(() => frame.remove());
+  const doc = frame.contentDocument.implementation.createHTMLDocument();
+  assert_equals(doc.URL, "about:blank");
+  assert_equals(doc.open(), doc);
+  assert_equals(doc.URL, "about:blank");
+}, "document.open() does not change document's URL (non-active document without an associated Window object)");