MediaFocusControl: fix comment

    /**

     * The stack of remote control event receivers.

     *  Code sections and methods that modify the remote control event receiver stack are

     *  synchronized on mPRStack, but also BEFORE on mFocusLock as any change in either

     *  stack, audio focus or RC, can lead to a change in the remote control display

     * All read and write operations on mPRStack are synchronized.

     */

    private final Stack<PlayerRecord> mPRStack = new Stack<PlayerRecord>();