Added CSSPropertyAPI and CSS padding properties which implement this API

third_party/WebKit/Source/core/css/properties/CSSPropertyAPI.h

+// Copyright 2016 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.
+
+#ifndef CSSPropertyAPI_h
+#define CSSPropertyAPI_h
+
+#include "core/CSSPropertyNames.h"
+#include "core/css/CSSValue.h"
+#include "core/css/parser/CSSParserMode.h"
+#include "core/css/parser/CSSParserTokenRange.h"
+
+namespace blink {
+
+// We will use this API to represent all functions used for property-specific
+// logic inside the blink style engine. All specific properties are subclasses
+// of CSSPropertyAPI.
+//
+// To add a new property using this API:
+// - Make a class that implements CSSPropertyAPI, and implement the static
+//   methods.
+// - Update the cssPropertyDescriptors array in CSSPropertyDescriptor.cpp to
+//   call GET_DESCRIPTOR(classname).
+//
+// To add new functions using this API:
+// - New functions and static variables can be added in this class. A default
+//   implementation of functions can optionally be provided.
+// - When adding new functions, also add them to GET_DESCRIPTOR, and the get()
+//   method in CSSPropertyDescriptors.cpp, and the descriptor struct in
+//   CSSPropertyDescriptor.h.
+class CSSPropertyAPI {
+  STATIC_ONLY(CSSPropertyAPI);
+
+ public:
+  // Parses a single CSS property and returns the corresponding CSSValue. If the
+  // input is invalid it returns nullptr.
+  static const CSSValue* parseSingleValue(CSSParserTokenRange&,
+                                          const CSSParserContext&);
+};
+
+}  // namespace blink
+
+#endif  // CSSPropertyAPI_h