Introduce DocumentOrShadowRoot Mixin

third_party/WebKit/Source/core/dom/DocumentOrShadowRoot.idl

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// https://dom.spec.whatwg.org/#mixin-documentorshadowroot
+// http://w3c.github.io/webcomponents/spec/shadow/#extensions-to-the-documentorshadowroot-mixin
+[
+    LegacyTreatAsPartialInterface,
+    NoInterfaceObject,
+] interface DocumentOrShadowRoot {
+    // Selection API
+    // http://w3c.github.io/selection-api/#extensions-to-document-interface
+    Selection? getSelection();
+    // CSSOM View Module
+    // http://dev.w3.org/csswg/cssom-view/#extensions-to-the-document-interface
+    // TODO(philipj): The x and y arguments should be of type double.
+    Element? elementFromPoint(long x, long y);
+    sequence<Element> elementsFromPoint(long x, long y);
+    readonly attribute Element? activeElement;
+    [SameObject] readonly attribute StyleSheetList styleSheets;
+};