title: Issue with erasing canvas shape
body: <p>I am working on a doodle in canvas,</p>
  
  <p>I am running into an issue where when I erase the object by overdrawing it with the background color I am left with an outline of the original  shape. <img src="https://i.stack.imgur.com/kMmcP.png" alt="enter image description here"></p>
  
  <p><strong>Here is the code I am using</strong></p>
  
  <p><em>and yes I am not using clear rect because the circles can overlap.</em></p>
  
  <pre><code>    function erase(eraseColor) {
      ctx.fillStyle = ctx.strokeStyle = eraseColor || "#FFFFFF";
      drawCircle();
      ctx.fillStyle = ctx.strokeStyle = fillColor;
  }
  
  function drawCircle() {
      ctx.beginPath();
      ctx.arc(x, y, rad, 0, Math.PI * 2, true);
      ctx.closePath();
      ctx.fill();
  }
  </code></pre>