Implement standard interface for toggling experimental features

Summary: We want to start experimenting with changes to the library in a more controlled and easier to measure manner. This diff adds the basics of an experiment layer to csslayout.

Reviewed By: gkassabli

Differential Revision: D4174260

fbshipit-source-id: ad3667183810c02833fba9a1276f89286e848fcd

csharp/Facebook.CSSLayout/CSSExperimentalFeature.cs

@@ -0,0 +1,15 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+namespace Facebook.CSSLayout
+{
+    public enum CSSExperimentalFeature
+    {
+    }
+}

csharp/Facebook.CSSLayout/CSSNode.cs

@@ -550,5 +550,17 @@ namespace Facebook.CSSLayout
         {
             return Native.CSSNodeGetInstanceCount();
         }
+
+        public static void setExperimentalFeatureEnabled(
+            CSSExperimentalFeature feature,
+            bool enabled)
+        {
+            return Native.CSSLayoutSetExperimentalFeatureEnabled(feature, enabled);
+        }
+
+        public static bool isExperimentalFeatureEnabled(CSSExperimentalFeature feature)
+        {
+            return Native.CSSLayoutIsExperimentalFeatureEnabled(feature);
+        }
     }
 }

csharp/Facebook.CSSLayout/Native.cs

@@ -37,7 +37,13 @@ namespace Facebook.CSSLayout
         public static extern void CSSNodeReset(IntPtr cssNode);
 
         [DllImport(DllName)]
-        public static extern int CSSNodeGetInstanceCount();
+        public static extern void CSSLayoutSetExperimentalFeatureEnabled(
+            CSSExperimentalFeature feature,
+            bool enabled);
+
+        [DllImport(DllName)]
+        public static extern bool CSSLayoutIsExperimentalFeatureEnabled(
+            CSSExperimentalFeature feature);
 
         [DllImport(DllName)]
         public static extern void CSSNodeInsertChild(IntPtr node, IntPtr child, uint index);