为什么 Chart.js 画布不考虑容器元素的填充？

var options = {
    maintainAspectRatio: false,
    responsive: true
};

var data = {
    labels: ["", "", "", "", "", "", ""],
    datasets: [
        {
            label: "My First dataset",
            fillColor: "rgba(220,220,220,0.2)",
            strokeColor: "rgba(220,220,220,1)",
            pointColor: "rgba(220,220,220,1)",
            pointStrokeColor: "#fff",
            pointHighlightFill: "#fff",
            pointHighlightStroke: "rgba(220,220,220,1)",
            data: [65, 59, 80, 81, 56, 55, 40]
        },
        {
            label: "My Second dataset",
            fillColor: "rgba(151,187,205,0.2)",
            strokeColor: "rgba(151,187,205,1)",
            pointColor: "rgba(151,187,205,1)",
            pointStrokeColor: "#fff",
            pointHighlightFill: "#fff",
            pointHighlightStroke: "rgba(151,187,205,1)",
            data: [28, 48, 40, 19, 86, 27, 90]
        }
    ]
};

var ctx1 = document.getElementById("mychart1").getContext("2d");
var myNewChart = new Chart(ctx1).Line(data, options);

.container {
    padding: 15px 15px 15px 15px;
    width: 300px;
    height: 200px;
    border: 1px solid black;
}

.child {
    display: inline-block;
    border: 1px solid red;
    width:100%;
    height:100%;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/1.1.1/Chart.js"></script>


<div class='container'>
    <canvas id='mychart1' class='child'></canvas>
</div>
<br>
<div class='container'>
    <div class='child'>test</div>
</div>