Summary
-------

Add explicit constructors to some classes in Java Sound APIs which using default constructors.

Problem
-------

Default constructors are not recommended for formal API classes.

Solution
--------

Add the public constructors to the public/non-abstract classes, and protected constructors to the public/abstract classes.

Specification
-------------

    src/java.desktop/share/classes/javax/sound/midi/VoiceStatus.java	
         public int volume = 0;
    +
    +    /**
    +     * Constructs a {@code VoiceStatus}.
    +     */
    +    public VoiceStatus() {}
     }

    src/java.desktop/share/classes/javax/sound/midi/spi/MidiDeviceProvider.java
        public abstract class MidiDeviceProvider {
 
    +    /**
    +     * Constructs a {@code MidiDeviceProvider}.
    +     */
    +    protected MidiDeviceProvider() {}

    src/java.desktop/share/classes/javax/sound/midi/spi/MidiFileReader.java
        public abstract class MidiFileReader {
 
    +    /**
    +     * Constructs a {@code MidiFileReader}.
    +     */
    +    protected MidiFileReader() {}

    src/java.desktop/share/classes/javax/sound/midi/spi/MidiFileWriter.java	         
        public abstract class MidiFileWriter {
 
    +    /**
    +     * Constructs a {@code MidiFileWriter}.
    +     */
    +    protected MidiFileWriter() {}

    src/java.desktop/share/classes/javax/sound/midi/spi/SoundbankReader.java
        public abstract class SoundbankReader {
 
    +    /**
    +     * Constructs a {@code SoundbankReader}.
    +     */
    +    protected SoundbankReader() {}

    src/java.desktop/share/classes/javax/sound/sampled/spi/AudioFileReader.java
        public abstract class AudioFileReader {
 
    +    /**
    +     * Constructs a {@code AudioFileReader}.
    +     */
    +    protected AudioFileReader() {}

    src/java.desktop/share/classes/javax/sound/sampled/spi/AudioFileWriter.java
        public abstract class AudioFileWriter {
 
    +    /**
    +     * Constructs a {@code AudioFileWriter}.
    +     */
    +    protected AudioFileWriter() {}

    src/java.desktop/share/classes/javax/sound/sampled/spi/FormatConversionProvider.java
        public abstract class FormatConversionProvider {
 
    +    /**
    +     * Constructs a {@code FormatConversionProvider}.
    +     */
    +    protected FormatConversionProvider() {}

    src/java.desktop/share/classes/javax/sound/sampled/spi/MixerProvider.java
        public abstract class MixerProvider {
 
    +    /**
    +     * Constructs a {@code MixerProvider}.
    +     */
    +    protected MixerProvider() {}

Link for convenience:
    http://cr.openjdk.java.net/~serb/8250858/webrev.00/