8325189: Enable this-escape javac warning in java.base

Reviewed-by: alanb, erikj, naoto, smarks, ihse, joehw, lancea, weijun

src/java.base/share/classes/java/util/EnumMap.java

@@ -165,6 +165,7 @@ public class EnumMap<K extends Enum<K>, V> extends AbstractMap<K, V>
      *     {@code EnumMap} instance and contains no mappings
      * @throws NullPointerException if {@code m} is null
      */
+    @SuppressWarnings("this-escape")
     public EnumMap(Map<K, ? extends V> m) {
         if (m instanceof EnumMap) {
             EnumMap<K, ? extends V> em = (EnumMap<K, ? extends V>) m;