views: Add support for absolute positioned overlay views.

To test:
Run `cefclient.exe --use-views --hide-frame --hide-controls`
Add `--enable-chrome-runtime` for the same behavior using the Chrome location
bar instead of a text field.

libcef/browser/chrome/views/chrome_views_util.cc

@@ -0,0 +1,15 @@
+// Copyright 2021 The Chromium Embedded Framework Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be found
+// in the LICENSE file.
+
+#include "libcef/browser/chrome/views/chrome_views_util.h"
+
+#include "libcef/browser/views/view_util.h"
+
+namespace cef {
+
+bool IsCefView(views::View* view) {
+  return view_util::GetFor(view, /*find_known_parent=*/false) != nullptr;
+}
+
+}  // namespace cef