title: content_main.xml vs activity_main.xml
body: <p>I have recently updated android studio to 1.4 and noticed that there is now a <code>content_main.xml</code> and an <code>activity_main.xml</code>. It seems that content_main deals with what goes into the app and activity_main deals with the layout/display of the widgets from content_main, I am not sure whether this is correct? Also would it be possible for anyone to explain why having activity_main deal with just the layout is better and why Google decided to do this split?</p>
  
  <p>All help is much appreciated.</p>