First version of PerformanceObserver

Source/core/timing/PerformanceObserver.idl

Index: Source/core/timing/PerformanceObserver.idl
diff --git a/Source/core/timing/PerformanceObserver.idl b/Source/core/timing/PerformanceObserver.idl
new file mode 100644
index 0000000000000000000000000000000000000000..de04cb9eb7a449aad9654929ecc7f4a4b15bb127
--- /dev/null
+++ b/Source/core/timing/PerformanceObserver.idl
@@ -0,0 +1,16 @@
+// Copyright 2015 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.
+
+// http://w3c.github.io/performance-timeline/#idl-def-PerformanceObserverCallback
+callback PerformanceObserverCallback = void (PerformanceObserverEntryList entries, PerformanceObserver observer);
+
+// http://w3c.github.io/performance-timeline/#the-performance-observer-interface
+[
+    CustomConstructor(PerformanceObserverCallback callback),
+    RuntimeEnabled=PerformanceObserver,
+    GarbageCollected,
+] interface PerformanceObserver {
+    [RaisesException] void observe(PerformanceObserverInit options);
+    void disconnect();
+};