IntersectionObserver: second cut.

third_party/WebKit/Source/core/dom/IntersectionObserver.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.
+
+// TODO(szager): add link to final spec.
+callback IntersectionObserverCallback = void (sequence<IntersectionObserverEntry> entries, IntersectionObserver observer);
+
+// TODO(szager): Update the doc link when the spec has an official home.
+// https://github.com/slightlyoff/IntersectionObserver
+[
+    CustomConstructor(IntersectionObserverCallback callback, IntersectionObserverInit options),
+    GarbageCollected,
+    RuntimeEnabled=IntersectionObserver,
+] interface IntersectionObserver {
+    [RaisesException] void observe(Element target);
+    [RaisesException] void unobserve(Element target);
+    void disconnect();
+    sequence<IntersectionObserverEntry> takeRecords();
+};