Merge "Don't allow MemoryFiles of negative length."

     * Allocates a new ashmem region. The region is initially not purgable.

     *

     * @param name optional name for the file (can be null).

     * @param length of the memory file in bytes.

     * @param length of the memory file in bytes, must be non-negative.

     * @throws IOException if the memory file could not be created.

     */

    public MemoryFile(String name, int length) throws IOException {

        mLength = length;

        if (length >= 0) {

            mFD = native_open(name, length);

        } else {

            throw new IOException("Invalid length: " + length);

        }

        if (length > 0) {

            mAddress = native_mmap(mFD, length, PROT_READ | PROT_WRITE);

        } else {