8060485: (str) contentEquals checks the String contents twice on mismatch

Reviewed-by: martin, chegar, alanb

src/share/classes/java/lang/String.java

@@ -1045,8 +1045,9 @@ public final class String
             }
         }
         // Argument is a String
-        if (cs.equals(this))
-            return true;
+        if (cs instanceof String) {
+            return equals(cs);
+        }
         // Argument is a generic CharSequence
         char v1[] = value;
         int n = v1.length;