assert that ShadowNodeRegistry is only accessed from one thread

Reviewed By: astreet

Differential Revision: D3461859

fbshipit-source-id: 790e831d2ca239110e00a5723be40e870ceab020

ReactAndroid/src/main/java/com/facebook/react/common/SingleThreadAsserter.java

@@ -0,0 +1,29 @@
+/**
+ * Copyright (c) 2015-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.
+ */
+
+package com.facebook.react.common;
+
+import javax.annotation.Nullable;
+
+import com.facebook.infer.annotation.Assertions;
+
+/**
+ * Simple class for asserting that operations only run on a single thread.
+ */
+public class SingleThreadAsserter {
+  private @Nullable Thread mThread = null;
+
+  public void assertNow() {
+    Thread current = Thread.currentThread();
+    if (mThread == null) {
+      mThread = current;
+    }
+    Assertions.assertCondition(mThread == current);
+  }
+}