@mixin placeholder
    @if support-legacy-browser("firefox", "18")
        &:-moz-placeholder
            @content

    @if support-legacy-browser("firefox", "19")
        &::-moz-placeholder
            @content

    @if support-legacy-browser("ie", "10")
        &:-ms-input-placeholder
            @content

    &::-webkit-input-placeholder
        @content

    &::input-placeholder
        @content

@mixin placeholder
    @if support-legacy-browser("firefox", "18")
        &:-moz-placeholder
            @content

    @if support-legacy-browser("firefox", "19")
        &::-moz-placeholder
            @content

    @if support-legacy-browser("ie", "10")
        &:-ms-input-placeholder
            @content

    &::-webkit-input-placeholder
        @content

    &::input-placeholder
        @content

    &.placeholder
        @content

Add placeholder class to mixin to support JS ployfills
Add placeholder class to mixin to support JS ployfills