Implement parseShorthand API for property "margin".

Shorthand property "margin" is parsed by delegating parsing logic to 
its component longhands API, using ConsumeShorthandVia4LonghandsAPI.
This cl also serves as a use case of ConsumeShorthandVia4LonghandsAPI.

This cl contains the following changes
* Implemented of "margin" parseShorthand API.
* Changed the system to use the new API for parsing.
- Changed CSSPropertyParser.cpp to use property API to parse "margin".
- Added api parsing to json file.
- Updated BUILD files to include the new API files.

Bug: 668012
Change-Id: Ide0737ab44088cc882191b53278e56c65a075208
Reviewed-on: https://chromium-review.googlesource.com/560801
Commit-Queue: Jia Meng <jiameng@chromium.org>
Reviewed-by: Alan Cutter <alancutter@chromium.org>
Reviewed-by: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#485241}

third_party/WebKit/Source/core/BUILD.gn

@@ -593,6 +593,7 @@ css_properties("make_core_generated_css_property_apis") {
     "$blink_core_output_dir/css/properties/CSSShorthandPropertyAPIFlex.h",
     "$blink_core_output_dir/css/properties/CSSShorthandPropertyAPIFont.h",
     "$blink_core_output_dir/css/properties/CSSShorthandPropertyAPIFontVariant.h",
+    "$blink_core_output_dir/css/properties/CSSShorthandPropertyAPIMargin.h",
     "$blink_core_output_dir/css/properties/CSSShorthandPropertyAPIOverflow.h",
     "$blink_core_output_dir/css/properties/CSSShorthandPropertyAPIOffset.h",
     "$blink_core_output_dir/css/properties/CSSShorthandPropertyAPITextDecoration.h",

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

@@ -540,6 +540,7 @@ blink_core_sources("css") {
     "properties/CSSShorthandPropertyAPIFlex.cpp",
     "properties/CSSShorthandPropertyAPIFont.cpp",
     "properties/CSSShorthandPropertyAPIFontVariant.cpp",
+    "properties/CSSShorthandPropertyAPIMargin.cpp",
     "properties/CSSShorthandPropertyAPIOffset.cpp",
     "properties/CSSShorthandPropertyAPIOverflow.cpp",
     "properties/CSSShorthandPropertyAPITextDecoration.cpp",

third_party/WebKit/Source/core/css/CSSProperties.json5

@@ -3782,6 +3782,8 @@
     {
       name: "margin",
       longhands: ["margin-top", "margin-right", "margin-bottom", "margin-left"],
+      api_class: true,
+      api_methods: ["parseShorthand"],
     },
     {
       name: "marker",

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

@@ -2377,8 +2377,6 @@ bool CSSPropertyParser::ParseShorthand(CSSPropertyID unresolved_property,
     case CSSPropertyTextDecoration:
       DCHECK(RuntimeEnabledFeatures::CSS3TextDecorationsEnabled());
       return ConsumeShorthandGreedily(textDecorationShorthand(), important);
-    case CSSPropertyMargin:
-      return Consume4Values(marginShorthand(), important);
     case CSSPropertyPadding:
       return Consume4Values(paddingShorthand(), important);
     case CSSPropertyWebkitTextEmphasis:

third_party/WebKit/Source/core/css/properties/CSSShorthandPropertyAPIMargin.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/CSSShorthandPropertyAPIMargin.h"
+
+#include "core/StylePropertyShorthand.h"
+#include "core/css/parser/CSSPropertyParserHelpers.h"
+
+namespace blink {
+
+bool CSSShorthandPropertyAPIMargin::parseShorthand(
+    bool important,
+    CSSParserTokenRange& range,
+    const CSSParserContext& context,
+    const CSSParserLocalContext& local_context,
+    HeapVector<CSSProperty, 256>& properties) {
+  return CSSPropertyParserHelpers::ConsumeShorthandVia4LonghandsAPI(
+      marginShorthand(), important, context, range, properties);
+}
+}  // namespace blink