Enable ServerTiming support

third_party/WebKit/Source/core/timing/PerformanceServerTiming.idl

Index: third_party/WebKit/Source/core/timing/PerformanceServerTiming.idl
diff --git a/third_party/WebKit/Source/core/timing/PerformanceServerTiming.idl b/third_party/WebKit/Source/core/timing/PerformanceServerTiming.idl
new file mode 100644
index 0000000000000000000000000000000000000000..7ef34cbed4542109ddb3a16fe7eb58777057650d
--- /dev/null
+++ b/third_party/WebKit/Source/core/timing/PerformanceServerTiming.idl
@@ -0,0 +1,10 @@
+// Copyright 2017 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.
+
+[
+    RuntimeEnabled=ServerTiming
+] interface PerformanceServerTiming : PerformanceEntry {
+    readonly attribute DOMString metric;
+    readonly attribute DOMString description;
+};