First version of PerformanceObserver

Source/core/timing/PerformanceObserverInit.idl

Index: Source/core/timing/PerformanceObserverInit.idl
diff --git a/Source/core/timing/PerformanceObserverInit.idl b/Source/core/timing/PerformanceObserverInit.idl
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index 0000000000000000000000000000000000000000..635a31c79ef39b5ff1272408ec6bc19235db8bc4
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+++ b/Source/core/timing/PerformanceObserverInit.idl
@@ -0,0 +1,10 @@
+// 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/#the-performance-observer-interface
+[
+    RuntimeEnabled=PerformanceObserver,
+] dictionary PerformanceObserverInit {
+    required sequence<DOMString> entryTypes;
+};