Added CSSPropertyTransitionPropertyUtils which holds shared parsing logic.

third_party/WebKit/Source/core/css/properties/CSSPropertyTransitionPropertyUtils.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/CSSPropertyTransitionPropertyUtils.h"
+
+#include "core/CSSPropertyNames.h"
+#include "core/CSSValueKeywords.h"
+#include "core/css/CSSCustomIdentValue.h"
+#include "core/css/CSSIdentifierValue.h"
+#include "core/css/CSSPropertyMetadata.h"
+#include "core/css/CSSValue.h"
+#include "core/css/CSSValueList.h"
+#include "core/css/parser/CSSParserToken.h"
+#include "core/css/parser/CSSParserTokenRange.h"
+#include "core/css/parser/CSSPropertyParserHelpers.h"
+
+namespace blink {
+
+CSSValue* CSSPropertyTransitionPropertyUtils::ConsumeTransitionProperty(
+    CSSParserTokenRange& range) {
+  const CSSParserToken& token = range.Peek();
+  if (token.GetType() != kIdentToken)
+    return nullptr;
+  if (token.Id() == CSSValueNone)
+    return CSSPropertyParserHelpers::ConsumeIdent(range);
+  CSSPropertyID unresolved_property = token.ParseAsUnresolvedCSSPropertyID();
+  if (unresolved_property != CSSPropertyInvalid &&
+      unresolved_property != CSSPropertyVariable) {
+    DCHECK(CSSPropertyMetadata::IsEnabledProperty(unresolved_property));
+    range.ConsumeIncludingWhitespace();
+    return CSSCustomIdentValue::Create(unresolved_property);
+  }
+  return CSSPropertyParserHelpers::ConsumeCustomIdent(range);
+}
+
+bool CSSPropertyTransitionPropertyUtils::IsValidPropertyList(
+    const CSSValueList& value_list) {
+  if (value_list.length() < 2)
+    return true;
+  for (auto& value : value_list) {
+    if (value->IsIdentifierValue() &&
+        ToCSSIdentifierValue(*value).GetValueID() == CSSValueNone)
+      return false;
+  }
+  return true;
+}
+
+}  // namespace blink