Introduce KeyframeEffectReadOnly interface

third_party/WebKit/Source/core/animation/KeyframeEffectReadOnly.idl

Index: third_party/WebKit/Source/core/animation/KeyframeEffectReadOnly.idl
diff --git a/third_party/WebKit/Source/core/animation/KeyframeEffectReadOnly.idl b/third_party/WebKit/Source/core/animation/KeyframeEffectReadOnly.idl
new file mode 100644
index 0000000000000000000000000000000000000000..f270b2b5e27a840f782944b10bd85b9f2fb0ce03
--- /dev/null
+++ b/third_party/WebKit/Source/core/animation/KeyframeEffectReadOnly.idl
@@ -0,0 +1,15 @@
+// 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://w3c.github.io/web-animations/#the-keyframeeffect-interfaces
+
+[
+    // TODO(dstockwell): the third argument should be "optional (unrestricted double or KeyframeEffectOptions) timing".
+    Constructor(Element? target, (sequence<Dictionary> or Dictionary)? effect, optional unrestricted double timing),
+    Constructor(Element? target, (sequence<Dictionary> or Dictionary)? effect, KeyframeEffectOptions timing),
+    ConstructorCallWith=ExecutionContext,
+    RaisesException=Constructor,
+    RuntimeEnabled=WebAnimationsAPI,
+] interface KeyframeEffectReadOnly : AnimationEffectReadOnly {
+};