8319925: CSS.BackgroundImage incorrectly uses double-checked locking

Reviewed-by: aivanov

Author: prsadhuk

src/java.desktop/share/classes/javax/swing/text/html/CSS.java

@@ -2933,8 +2933,8 @@ public boolean equals(Object val) {
      */
     @SuppressWarnings("serial") // Same-version serialization only
     static class BackgroundImage extends CssValue {
-        private boolean    loadedImage;
-        private ImageIcon  image;
+        private volatile boolean loadedImage;
+        private ImageIcon image;
 
         Object parseCssValue(String value) {
             BackgroundImage retValue = new BackgroundImage();
@@ -2952,14 +2952,14 @@ ImageIcon getImage(URL base) {
                 synchronized(this) {
                     if (!loadedImage) {
                         URL url = CSS.getURL(base, svalue);
-                        loadedImage = true;
                         if (url != null) {
                             image = new ImageIcon();
                             Image tmpImg = Toolkit.getDefaultToolkit().createImage(url);
                             if (tmpImg != null) {
                                 image.setImage(tmpImg);
                             }
                         }
+                        loadedImage = true;
                     }
                 }
             }