Sync of methods reading the properties map.

Co-authored-by: Martin Balao Alonso <[email protected]>
Co-authored-by: Francisco Ferrari Bihurriet <[email protected]>

Author: martinuy

src/java.base/share/classes/java/security/Provider.java

@@ -429,7 +429,7 @@ public synchronized Set<Map.Entry<Object,Object>> entrySet() {
      * @since 1.2
      */
     @Override
-    public Set<Object> keySet() {
+    public synchronized Set<Object> keySet() {
         checkInitialized();
         return Collections.unmodifiableSet(super.keySet());
     }
@@ -441,7 +441,7 @@ public Set<Object> keySet() {
      * @since 1.2
      */
     @Override
-    public Collection<Object> values() {
+    public synchronized Collection<Object> values() {
         checkInitialized();
         return Collections.unmodifiableCollection(super.values());
     }
@@ -672,7 +672,8 @@ public synchronized Enumeration<Object> elements() {
     }
 
     // let javadoc show doc from superclass
-    public String getProperty(String key) {
+    @Override
+    public synchronized String getProperty(String key) {
         checkInitialized();
         return super.getProperty(key);
     }