Exit PIP on unload in the demo.

When unloading content (e.g. when closing or when deleting offline
content), we should exit the PIP window and fullscreen.  This moves
these actions to the unload() method so they affect other sources of
unloads.

Fixes #2055

Change-Id: Ie1b5ac0f7cb814ff6bae3b08cc4c1fc80967d941

demo/close_button.js

@@ -39,12 +39,6 @@ shakaDemo.CloseButton = class extends shaka.ui.Element {
     this.parent.appendChild(this.button_);
 
     this.button_.addEventListener('click', () => {
-      if (document.fullscreenElement) {
-        document.exitFullscreen();
-      }
-      if (document.pictureInPictureElement) {
-        document.exitPictureInPicture();
-      }
       shakaDemoMain.unload();
     });
 

demo/main.js

@@ -845,6 +845,12 @@ shakaDemo.Main = class {
     this.hideNode_(videoBar);
     this.video_.poster = shakaDemo.Main.mainPoster_;
 
+    if (document.fullscreenElement) {
+      document.exitFullscreen();
+    }
+    if (document.pictureInPictureElement) {
+      document.exitPictureInPicture();
+    }
     this.player_.unload();
 
     // The currently-selected asset changed, so update asset cards.