Extremely minor CSS fixes to the desktop User Manager

chrome/browser/resources/user_manager/control_bar.css

Index: chrome/browser/resources/user_manager/control_bar.css
diff --git a/chrome/browser/resources/user_manager/control_bar.css b/chrome/browser/resources/user_manager/control_bar.css
index 16ceaf279335ade88ca71b2a46c61cd91e41a1ab..6a2838cbbcf5264c5277edec19d85e4cbea6dc5c 100644
--- a/chrome/browser/resources/user_manager/control_bar.css
+++ b/chrome/browser/resources/user_manager/control_bar.css
@@ -23,6 +23,7 @@
 
 .header-bar-item {
   display: inline-block;
+  font-size: 12px;
 }
 
 html[dir=rtl] .header-bar-item {
@@ -59,9 +60,9 @@ html[dir=rtl] #login-header-bar #guest-user-button {
   background-position: left center;
   background-repeat: no-repeat;
   border: none;
+  border-radius: 0;
   box-shadow: none;
   cursor: pointer;
-  font-size: 12px;
   opacity: 0.8;
 }