Update overlay cast buttons for clank, part 1 of 3.

Source/core/css/mediaControlsNew.css

 /*
  * Copyright (C) 2009 Apple Inc.  All rights reserved.
  * Copyright (C) 2015 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 138 matching lines @@
     background-color: transparent;
     width: 100%;
     height: 100%;
     padding: 0;
 }
 
 video::-internal-media-controls-overlay-cast-button {
     -webkit-appearance: -internal-media-overlay-cast-off-button;
     display: flex;
     position: absolute;
-    top: 5%;
-    left: 5%;
+    top: 8px;
+    left: 8px;
     margin-left: 0px;
     margin-top: 0px;
     border: none;
     background-color: transparent;
     width: 48px;
     height: 48px;
     padding: 0;
     transition: opacity 0.3s;
 }
 
@@ skipping 264 matching lines @@
     font-weight: bold;
 }
 
 video::-webkit-media-text-track-container u {
     text-decoration: underline;
 }
 
 video::-webkit-media-text-track-container i {
     font-style: italic;
 }