title: how could I get default sms app's package name?
body: <p>As default sms app is added in 4.4, I cannot open default sms app like this:</p>
  
  <pre><code>Intent intent = new Intent(Intent.ACTION_MAIN);
  intent.addCategory(Intent.CATEGORY_DEFAULT);
  intent.setType("vnd.android-dir/mms-sms");
  startActivity(intent);
  </code></pre>
  
  <p>So how could I get default sms app's package name, so I can open it from my app directly?</p>