Adding 'transform-symbol-member' transform to preset.

babel-preset/configs/main.js

@@ -36,6 +36,7 @@ module.exports = {
     'transform-react-jsx',
     'transform-regenerator',
     ['transform-es2015-for-of', { loose: true }],
+    require('../transforms/transform-symbol-member'),
   ]),
   retainLines: true,
   sourceMaps: false,

babel-preset/package.json

@@ -1,6 +1,6 @@
 {
   "name": "babel-preset-react-native",
-  "version": "1.2.4",
+  "version": "1.4.0",
   "description": "Babel preset for React Native applications",
   "main": "index.js",
   "repository": "https://github.com/facebook/react-native/tree/master/babel-preset",

babel-preset/transforms/transform-symbol-member.js

@@ -0,0 +1,61 @@
+/**
+ * Copyright 2004-present Facebook. All Rights Reserved.
+ */
+
+'use strict';
+
+/*eslint consistent-return: 0*/
+
+/**
+ * Transforms function properties of the `Symbol` into
+ * the presence check, and fallback string "@@<name>".
+ *
+ * Example:
+ *
+ *   Symbol.iterator;
+ *
+ * Transformed to:
+ *
+ *   typeof Symbol.iterator === 'function' ? Symbol.iterator : '@@iterator';
+ */
+module.exports = function symbolMember(babel) {
+  const t = babel.types;
+
+  return {
+    visitor: {
+      MemberExpression(path) {
+        let node = path.node;
+
+        if (!isAppropriateMember(node)) {
+          return;
+        }
+
+        path.replaceWith(
+          t.conditionalExpression(
+            t.binaryExpression(
+              '===',
+              t.unaryExpression(
+                'typeof',
+                t.identifier('Symbol'),
+                true
+              ),
+              t.stringLiteral('function')
+            ),
+            node,
+            t.stringLiteral(`@@${node.property.name}`)
+          )
+        );
+
+        // We should stop to avoid infinite recursion, since Babel
+        // traverses replaced path, and again would hit our transform.
+        path.stop();
+      },
+    },
+  };
+};
+
+function isAppropriateMember(node) {
+  return node.object.type === 'Identifier' &&
+    node.object.name === 'Symbol' &&
+    node.property.type === 'Identifier';
+}