Move DebugEnvironment helper to open source

Summary:
This is an internal only module that we use to detect whether we are in async debugging mode.

Changelog: [Internal]

Reviewed By: yungsters

Differential Revision: D20879780

fbshipit-source-id: 5915f4e1c54a3fda0cf607c77f463120264fdbc4

Libraries/Utilities/DebugEnvironment.js

@@ -0,0 +1,21 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+'use strict';
+
+export let isAsyncDebugging: boolean = false;
+
+if (__DEV__) {
+  // These native interfaces don't exist in asynchronous debugging environments.
+  isAsyncDebugging =
+    !global.nativeExtensions &&
+    !global.nativeCallSyncHook &&
+    !global.RN$Bridgeless;
+}