Implemented CSSPropertyAPI for text-underline-position property.

Added CSSPropertyAPITextUnderlinePosition which implements
CSSPropertyAPI for the text-underline-position property.
Parsing logic is the same as before, just was moved from
CSSPropertyParser to the .cpp file. Added flag to
CSSProperties.in so that the .h file will be generated.

BUG=668012

Review-Url: https://codereview.chromium.org/2614903002
Cr-Commit-Position: refs/heads/master@{#441879}

third_party/WebKit/Source/core/css/BUILD.gn

@@ -344,6 +344,7 @@ blink_core_sources("css") {
     "parser/SizesAttributeParser.cpp",
     "parser/SizesCalcParser.cpp",
     "properties/CSSPropertyAPI.h",
+    "properties/CSSPropertyAPITextUnderlinePosition.cpp",
     "properties/CSSPropertyAPITransformOrigin.cpp",
     "properties/CSSPropertyAPITranslate.cpp",
     "properties/CSSPropertyAPIWebkitPadding.cpp",

third_party/WebKit/Source/core/css/CSSProperties.in

@@ -384,7 +384,7 @@ text-overflow type_name=TextOverflow
 text-shadow interpolable, inherited, converter=convertShadowList
 text-size-adjust inherited, converter=convertTextSizeAdjust, type_name=TextSizeAdjust
 text-transform inherited, keyword_only, keywords=[capitalize|uppercase|lowercase|none], initial_keyword=none
-text-underline-position runtime_flag=CSS3TextDecorations, inherited, type_name=TextUnderlinePosition
+text-underline-position runtime_flag=CSS3TextDecorations, inherited, type_name=TextUnderlinePosition, api_class
 top typedom_types=[Length], keywords=[auto], supports_percentage, interpolable, initial=initialOffset, converter=convertLengthOrAuto
 touch-action converter=convertFlags<TouchAction>, type_name=TouchAction
 transform typedom_types=[Transform], keywords=[none], interpolable, converter=convertTransformOperations

third_party/WebKit/Source/core/css/parser/CSSPropertyParser.cpp

@@ -3709,11 +3709,6 @@ const CSSValue* CSSPropertyParser::parseSingleValue(
       return consumeInteger(m_range, 0);
     case CSSPropertyOrder:
       return consumeInteger(m_range);
-    case CSSPropertyTextUnderlinePosition:
-      // auto | [ under || [ left | right ] ], but we only support auto | under
-      // for now
-      ASSERT(RuntimeEnabledFeatures::css3TextDecorationsEnabled());
-      return consumeIdent<CSSValueAuto, CSSValueUnder>(m_range);
     case CSSPropertyVerticalAlign:
       return consumeVerticalAlign(m_range, m_context.mode());
     case CSSPropertyShapeOutside:

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