Edit in JSFiddle

.header {
    width:100%;
    background-color:red;
    position:relative;
    padding:20px;
    box-sizing:border-box;
}
.inlineList li {
    display:inline-block;
    margin: 0 0 0 10px;
    border-radius:0 10px 10px 0;
}
.inlineList li:first-of-type {
    margin:0;
}
.inlineList {
    padding:10px;
    background-color:black;
    position:relative;
}
.inlineList {
}
.socialIcons {
}
.socialIconsHolder {
    position:absolute;
    right:15px;
    bottom:0;
    overflow:hidden;
    padding:0 10px;
}
.icons:before, .icons:after {
    position: absolute;
    bottom: 0;
    width: 10px;
    height: 10px;
    content:" ";
}
.icons:before {
    left: -10px;
}
.icons:after {
    right: -10px;
}
.icons:after, .icons:before {
    border: 1px solid #252525;
}
.icons {
    border-top-left-radius: 10px;
    border-top-right-radius: 10px;
}
.icons:before {
    border-bottom-right-radius: 10px;
    border-width: 0 1px 1px 0;
}
.icons:after {
    border-bottom-left-radius: 10px;
    border-width: 0 0 1px 1px;
}
.icons:before {
    box-shadow: 2px 2px 0 #231F20;
}
.icons:after {
    box-shadow: -2px 2px 0 #231F20;
}
@media only screen and (max-width : 420px) {
    .socialIconsHolder {
        bottom: -54px;
    }
    .icons:before, .icons:after {
        position: absolute;
        top: 0;
        width: 10px;
        height: 10px;
        content:" ";
    }
    .icons:before {
        left: -10px;
    }
    .icons:after {
        right: -10px;
    }
    .icons:after, .icons:before {
        border: 1px solid #252525;
    }
    .icons {
        border-top-left-radius: 0;
        border-top-right-radius: 0;
        border-bottom-left-radius: 10px;
        border-bottom-right-radius: 10px;
    }
    .icons:before {
        border-bottom-right-radius: 0;
        border-top-right-radius: 10px;
        border-width: 1px 1px 0 0;
    }
    .icons:after {
        border-bottom-left-radius: 0;
        border-top-left-radius: 10px;
        border-width: 1px 0 0 1px;
    }
    .icons:before {
        box-shadow: 2px -2px 0 #252525;
    }
    .icons:after {
        box-shadow: -2px -2px 0 #252525;
    }
}