Add SecurityException.

Change-Id: Id41b7288e8f59e9f3427ab81be7815099a1b198e
diff --git a/user/super/com/google/gwt/emul/java/lang/SecurityException.java b/user/super/com/google/gwt/emul/java/lang/SecurityException.java
new file mode 100644
index 0000000..b864e1c
--- /dev/null
+++ b/user/super/com/google/gwt/emul/java/lang/SecurityException.java
@@ -0,0 +1,28 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package java.lang;
+
+/**
+ * See <a href="http://java.sun.com/j2se/1.5.0/docs/api/java/lang/SecurityException.html">the
+ * official Java API doc</a> for details.
+ * 
+ * This exception is never thrown by GWT or GWT's libraries, as GWT does not have a SecurityManager.
+ * It is provided in GWT only for compatibility with user code that explicitly catches it.
+ */
+public class SecurityException extends RuntimeException {
+  private SecurityException() {
+  }
+}