Implements CSSPropertyAPI for the text-underline-position property.

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

Index: third_party/WebKit/Source/core/css/properties/CSSPropertyAPITextUnderlinePosition.cpp
diff --git a/third_party/WebKit/Source/core/css/properties/CSSPropertyAPITextUnderlinePosition.cpp b/third_party/WebKit/Source/core/css/properties/CSSPropertyAPITextUnderlinePosition.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..5a6ce600a20e5f24199c7e6168c3214ab7270c06
--- /dev/null
+++ b/third_party/WebKit/Source/core/css/properties/CSSPropertyAPITextUnderlinePosition.cpp
@@ -0,0 +1,25 @@
+// 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/CSSPropertyAPITextUnderlinePosition.h"
+
+#include "core/css/parser/CSSPropertyParserHelpers.h"
+#include "platform/RuntimeEnabledFeatures.h"
+
+namespace blink {
+
+const CSSValue* CSSPropertyAPITextUnderlinePosition::parseSingleValue(
+    CSSParserTokenRange& range,
+    const CSSParserContext& context) {
+  // auto | [ under || [ left | right ] ], but we only support auto | under
+  // for now
+  DCHECK(RuntimeEnabledFeatures::css3TextDecorationsEnabled());
+  // auto | [ under || [ left | right ] ], but we only support auto | under
+  // for now
+  DCHECK(RuntimeEnabledFeatures::css3TextDecorationsEnabled());
+  return CSSPropertyParserHelpers::consumeIdent<CSSValueAuto, CSSValueUnder>(
+      range);
+}
+
+}  // namespace blink