title: Android 4.2 Stock browser. Canvas clearRect() sometimes doesn't work
body: <p>So I have a problem with <code>clearRect</code> in js-canvas-animation. This problem happens only on Android API 16, and only in the moment when animation is restart.</p>
  
  <p>I'm using <code>setInterval()</code> for my animation (here is simplify code)</p>
  
  <pre><code>function start() {   
      clearInterval(animationInterval);
      x = 0;
      canvas = document.getElementById("animationCanvas");
      ctx = canvas.getContext("2d");
      animationInterval = setInterval(func, 30);
  }
  
  function func() {
      ctx.clearRect(0, 0, canvas.width, canvas.height);
      ctx.fillRect(halfWidth - x, 0, 250, 150);
      x += extensionStep;
  }
  </code></pre>
  
  <p>It is look like a shore. But every time, when i restart animation with help start function, under new animation i see last frame previous animation. Already i was trying <code>beginPath()</code>, <code>save</code>, <code>stroke</code>. I check all question on SO and nothing.</p>
  
  <p>How i can clear the background under animation?</p>