[SASS] Placeholder mixin

placeholder.scss

// Placeholder @mixin for Sass
//
// A mixin to style placeholders in HTML5 form elements.
// Includes also a .placeholder class to be used with a polyfill e.g.
// https://github.com/mathiasbynens/jquery-placeholder
// Requires Sass 3.2.
//
// Example usage (.scss):
// 
// input {
//   @include placeholder {
//     /* styles for placeholder here */
//   }
// }
//

@mixin placeholder {
    &::-webkit-input-placeholder {
        @content;
    }

    &:-moz-placeholder { /* Firefox 18- */
        @content;
    }

    &::-moz-placeholder {  /* Firefox 19+ */
        @content;
    }

    &:-ms-input-placeholder {
        @content;
    }
}