Implements CSSPropertyAPI for the fragmentation element properties.

third_party/WebKit/Source/core/css/properties/CSSPropertyAPIBoxGroup.cpp

+// 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.
+
+#include "core/css/properties/CSSPropertyAPIBoxGroup.h"
+
+#include "core/css/parser/CSSPropertyParserHelpers.h"
+
+namespace blink {
+
+const CSSValue* CSSPropertyAPIBoxGroup::parseSingleValue(

[sashab, 2017/01/19 00:41:59]

The naming of this one is hard. 'Widows' and 'orphans' are defined in
Fragmentation L3 https://drafts.csswg.org/css-break-3/#widows-orphans, and
box-ordinal-group is not defined at all (although MDN has a page on it here
claiming its part of flexbox -
https://developer.mozilla.org/en-US/docs/Web/CSS/box-ordinal-group)

'Box' is a bit misleading, I think a better choice is
'CSSPropertyAPIFragmentationGroup'. :)

[nainar, 2017/01/19 00:57:23]

Done

+    CSSParserTokenRange& range,
+    const CSSParserContext* context) {
+  return CSSPropertyParserHelpers::consumePositiveInteger(range);
+}
+
+}  // namespace blink