Added CSSPropertyAPI and CSS padding properties which implement this API

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

Index: third_party/WebKit/Source/core/css/properties/CSSPropertyDescriptor.h
diff --git a/third_party/WebKit/Source/core/css/properties/CSSPropertyDescriptor.h b/third_party/WebKit/Source/core/css/properties/CSSPropertyDescriptor.h
new file mode 100644
index 0000000000000000000000000000000000000000..e91e470b6dc3ddb3817cb0d6f22cf5d9fcca1300
--- /dev/null
+++ b/third_party/WebKit/Source/core/css/properties/CSSPropertyDescriptor.h
@@ -0,0 +1,29 @@
+// 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.
+
+#include "core/CSSPropertyNames.h"
+
+namespace blink {
+
+class CSSValue;
+class CSSParserTokenRange;
+class CSSParserContext;
+
+// Stores function pointers matching those declared in CSSPropertyAPI.
+struct CSSPropertyDescriptor {
+  const CSSValue* (*parseSingleValue)(CSSParserTokenRange&,
+                                      const CSSParserContext&);
+  CSSPropertyID id;
+
+  // Stores whether or not this descriptor is for a valid property. Do not
+  // access the contents of this descriptor unless this value is true.
+  bool isValid;

[ojan, 2016/12/07 00:48:57]

Is this just a temporary thing we need while we're transitioning? Will this go
away when we have transitioned all properties over?

[ojan, 2016/12/07 00:49:41]

In particular, I'm trying to understand the end state of the design. Will we
always need the branch for checking isValid or is that something we can remove
eventually?

[aazzam, 2016/12/07 02:16:42]

yep this will be removed eventually! and once the switch statement in
CSSPropertyParser.cpp is removed, we won't need the if statement anymore.
I added a TODO, does this look better?

+
+  // Returns the corresponding CSSPropertyDescriptor for a given CSSPropertyID.
+  // Use this function to access the API for a property. Returns a descriptor
+  // with isValid set to false if no descriptor exists for this ID.
+  static const CSSPropertyDescriptor& get(CSSPropertyID);
+};
+
+}  // namespace blink