title: flutter: `RouteAware.didPop()` not triggered using `PageView.animateToPage()`
body: <p>I'm working on page navigation, but noticed that swipe gesture <code>PageView.animateToPage()</code> does not trigger <code>RouteAware</code> callback <code>didPop()</code> when I leave a page, only <code>didPush()</code> gets called for the new page.</p>
  <h2>Expectation</h2>
  <p>When I implement a <code>Drawer</code>, calling</p>
  <pre class="lang-dart prettyprint-override"><code>Navigator.of(context).pop();
  </code></pre>
  <p>in the drawer triggers <code>didPop()</code> as expected.</p>
  <p>So I expect that as a higher-level API, <code>PageView</code> would encapsulate this well.
  But so far I only see <code>onPageChanged(index)</code> but this would be similar to <code>didPush()</code> unless I manage the index as a state myself.</p>
  <h2>Question</h2>
  <p>Is this by design?</p>