Enable highlight for non-button input fields.

guacamole/src/main/webapp/styles/login.css

@@ -21,6 +21,10 @@
     -webkit-tap-highlight-color: rgba(0,0,0,0);
 }
 
+input[type=checkbox], input[type=text], textarea {
+    -webkit-tap-highlight-color: rgba(128,192,128,0.5);
+}
+
 input[type=submit], button {
     -webkit-appearance: none;
 }