Steps to reproduce:

1. Provide Web App Manifest including following two entries
  "display": "fullscreen",
  "orientation": "landscape"

2. Add to home, then launch it

3. The page is launched, but orientation is not changed (keep on being portrait).


Note:
If display is standalone, orientation is correctly changed. Since fullscreen mode is expected to be more immersive than standalone (i.e., standalone is a fallback of fullscreen), this looks a little curious.

Also, I find some articles that explains fullscreen & landscape work (https://developers.google.com/web/updates/2014/11/Support-for-installable-web-apps-with-webapp-manifest-in-chrome-38-for-Android), I guess this is a regression.