Add close button to the supervised user pages.

chrome/browser/resources/chromeos/login/screen_supervised_user_creation.css

Index: chrome/browser/resources/chromeos/login/screen_supervised_user_creation.css
diff --git a/chrome/browser/resources/chromeos/login/screen_supervised_user_creation.css b/chrome/browser/resources/chromeos/login/screen_supervised_user_creation.css
index 0db1542be527e101b6472226e2a135b3e9b30ada..2cb1d879972f9f87c7a4b3ca2b9cc9ea1c93ef61 100644
--- a/chrome/browser/resources/chromeos/login/screen_supervised_user_creation.css
+++ b/chrome/browser/resources/chromeos/login/screen_supervised_user_creation.css
@@ -549,3 +549,52 @@ html[dir=rtl] #supervised-user-creation-flip-photo {
 .camera.live:not(.online) .supervised-user-creation-image-stream-area .spinner {
   display: block;
 }
+
+.custom-gaia-button {
+  background: transparent none;
+  background-position: center;
+  background-repeat: no-repeat;
+  border-radius: 50%;
+  height: 24px;
+  position: absolute;
+  top: 10px;
+  width: 24px;
+  z-index: 1;
+}
+
+.custom-gaia-button:hover {
+  cursor: pointer;
+}
+
+.custom-gaia-button:focus {
+  background: rgba(0,0,0,.16);
+  background-position: center;
+  background-repeat: no-repeat;
+  opacity: 0.75;
+}
+
+ /* Even more specificity than button.custom-appearance:focus:focus */
+.custom-gaia-button:focus:focus:focus {
+   border-color: transparent;
+}
+
+.custom-gaia-button:active {
+  background: rgba(0,0,0,.12);
+  background-position: center;
+  background-repeat: no-repeat;
+  opacity: 1.0;
+}
+
+#supervised-user-creation-close-button-item {
+  background-image: url(chrome://theme/IDR_LOGIN_CLOSE_BUTTTON_ON_WHITE);
+  right: 10px;
+}
+
+html[dir=rtl] #supervised-user-creation-close-button-item {
+  left: 10px;
+  right: auto;
+}
+
+#supervised-user-creation-close-button-item:disabled {
+  background-image: url(chrome://theme/IDR_LOGIN_CLOSE_BUTTTON_MASKED);
+}