Add SDK 29 sources.

Test: N/A
Change-Id: Iedb7a31029e003928eb16f7e69ed147e72bb6235
diff --git a/java/io/SerialCallbackContext.java b/java/io/SerialCallbackContext.java
new file mode 100644
index 0000000..4009087
--- /dev/null
+++ b/java/io/SerialCallbackContext.java
@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2006, 2012, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package java.io;
+
+/**
+ * Context during upcalls from object stream to class-defined
+ * readObject/writeObject methods.
+ * Holds object currently being deserialized and descriptor for current class.
+ *
+ * This context keeps track of the thread it was constructed on, and allows
+ * only a single call of defaultReadObject, readFields, defaultWriteObject
+ * or writeFields which must be invoked on the same thread before the class's
+ * readObject/writeObject method has returned.
+ * If not set to the current thread, the getObj method throws NotActiveException.
+ */
+final class SerialCallbackContext {
+    private final Object obj;
+    private final ObjectStreamClass desc;
+    /**
+     * Thread this context is in use by.
+     * As this only works in one thread, we do not need to worry about thread-safety.
+     */
+    private Thread thread;
+
+    public SerialCallbackContext(Object obj, ObjectStreamClass desc) {
+        this.obj = obj;
+        this.desc = desc;
+        this.thread = Thread.currentThread();
+    }
+
+    public Object getObj() throws NotActiveException {
+        checkAndSetUsed();
+        return obj;
+    }
+
+    public ObjectStreamClass getDesc() {
+        return desc;
+    }
+
+    public void check() throws NotActiveException {
+        if (thread != null && thread != Thread.currentThread()) {
+            throw new NotActiveException(
+                "expected thread: " + thread + ", but got: " + Thread.currentThread());
+        }
+    }
+
+    private void checkAndSetUsed() throws NotActiveException {
+        if (thread != Thread.currentThread()) {
+             throw new NotActiveException(
+              "not in readObject invocation or fields already read");
+        }
+        thread = null;
+    }
+
+    public void setUsed() {
+        thread = null;
+    }
+}