Normalize reftests

tests/reftests/overflow/overflow-transform.html

@@ -10,6 +10,7 @@
                 overflow: hidden;
                 position: relative;
                 border:2px solid #000;
+                height: 300px;
             }
             .img-1{
                 display: inline-block;
@@ -36,6 +37,8 @@
             }
             body {
                 font-family: Arial;
+                line-height: 17px;
+                font-size: 1em;
             }
         </style>