Android has a bug here :(, centering just won't work. You can use this polyfill: https://github.com/diy/jquery-placeholder and it supports the "force" attribute. That attribute makes it run even on browser that "support" placeholder, like android.
$('#myInput').placeholder({force:true});
Then use regular CSS to style the placeholder class provided by the plugin
.placeholder{
text-align: center;
}