Add outline files for StylePropertyMap.

third_party/WebKit/Source/core/css/cssom/StylePropertyMap.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.
+
+[
+    RuntimeEnabled=CSSTypedOM,
+    GarbageCollected
+] interface StylePropertyMap {
+    [RaisesException] void append(DOMString property, (StyleValue or sequence<StyleValue> or DOMString) value);
+    [RaisesException, ImplementedAs=remove] void delete(DOMString property);
+    StyleValue? get(DOMString property);
+    sequence<StyleValue> getAll(DOMString property);
+    boolean has(DOMString property);
+    [RaisesException] void set(DOMString property, (StyleValue or sequence<StyleValue> or DOMString) value);
+    iterable<DOMString, (StyleValue or sequence<StyleValue>)>;
+    sequence<DOMString> getProperties();
+};