8318113: CSS.BackgroundImage doesn't implement equals

Reviewed-by: aivanov, tr, prr

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

@@ -2965,6 +2965,17 @@ public class CSS implements Serializable {
             }
             return image;
         }
+
+        @Override
+        public int hashCode() {
+            return Objects.hashCode(svalue);
+        }
+
+        @Override
+        public boolean equals(Object val) {
+            return val instanceof CSS.BackgroundImage img
+                   && Objects.equals(svalue, img.svalue);
+        }
     }
 
     /**

test/jdk/javax/swing/text/html/CSS/CSSAttributeEqualityBug.java

@@ -31,7 +31,7 @@ import javax.swing.text.html.StyleSheet;
 
 /*
  * @test
- * @bug 7083187
+ * @bug 7083187 8318113
  * @summary  Verifies if CSS.CSSValue attribute is same
  * @run main CSSAttributeEqualityBug
  */
@@ -72,6 +72,9 @@ public class CSSAttributeEqualityBug {
             "background-position: 1em 2em",
 
             "border-width: medium",
+
+            "background-image: none",
+            "background-image: url(image.png)",
     };
 
     /**
@@ -86,6 +89,8 @@ public class CSSAttributeEqualityBug {
             {"margin-top: 42px", "margin-top: 22px"},
             {"margin-top: 42px", "margin-top: 42pt"},
             {"margin-top: 100%", "margin-top: 50%"},
+
+            {"background-image: none", "background-image: url(image.png)"},
     };
 
     private static final String[][] EQUALS_WITH_SPACE = {