LibWeb: Add the History object and stub pushState and replaceState

The spec allows us to optionally return from these for any reason.
Our reason is that we don't have all the infrastructure in place yet to
implement them.

Userland/Libraries/LibWeb/HTML/History.cpp

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/DOM/Document.h>
+#include <LibWeb/HTML/History.h>
+
+namespace Web::HTML {
+
+History::History(DOM::Document& document)
+    : m_associated_document(document)
+{
+}
+
+History::~History()
+{
+}
+
+// https://html.spec.whatwg.org/multipage/history.html#dom-history-pushstate
+DOM::ExceptionOr<void> History::push_state(JS::Value data, String const&, String const& url)
+{
+    // NOTE: The second parameter of this function is intentionally unused.
+    return shared_history_push_replace_state(data, url, IsPush::Yes);
+}
+
+// https://html.spec.whatwg.org/multipage/history.html#dom-history-replacestate
+DOM::ExceptionOr<void> History::replace_state(JS::Value data, String const&, String const& url)
+{
+    // NOTE: The second parameter of this function is intentionally unused.
+    return shared_history_push_replace_state(data, url, IsPush::No);
+}
+
+// https://html.spec.whatwg.org/multipage/history.html#shared-history-push/replace-state-steps
+DOM::ExceptionOr<void> History::shared_history_push_replace_state(JS::Value, String const&, IsPush)
+{
+    // 1. Let document be history's associated Document. (NOTE: Not necessary)
+
+    // 2. If document is not fully active, then throw a "SecurityError" DOMException.
+    if (!m_associated_document.is_fully_active())
+        return DOM::SecurityError::create("Cannot perform pushState or replaceState on a document that isn't fully active.");
+
+    // 3. Optionally, return. (For example, the user agent might disallow calls to these methods that are invoked on a timer,
+    //    or from event listeners that are not triggered in response to a clear user action, or that are invoked in rapid succession.)
+    dbgln("FIXME: Implement shared_history_push_replace_state.");
+    return {};
+
+    // FIXME: Add the rest of the spec steps once they're added.
+}
+
+}