Layout problems in rooms when rotating

Testing Riot 0.4.0 on iPad Mini 4 running iOS 10.3.2.

These steps reproduce four problems which I'll bundle together:
* When you make a room full screen, the back button does not appear until you perform a rotate
* When you make a room full screen from portrait, messages are missing/truncated until you perform a rotate
* When you go "back" from a full screen room, both the back and full screen buttons are displayed simultaneously in the tool bar, until you either rotate or reopen the room.
* When you go "back" from full screen, you are not fully scrolled to the bottom any more.

Start off with a room in portrait mode:


Go full screen. Note the missing back button, and the fact that everything's truncated to the left part of the screen and some messages are missing:


Rotate to landscape to make the messages display correctly, plus the back button:


Back to portrait, all fine:


Now press the back button, and I get both buttons at once in the toolbar and I am scrolled back some distance whereas I was previously at the bottom:


Reproduce the four layout and scrolling problems in a room on an iPad Mini 4 running iOS 10.3.2, following the portrait, full-screen, rotation, and back-navigation steps in the report. Trace the room view's orientation and toolbar updates, then verify that all controls, messages, and the bottom scroll position remain correct without requiring rotation.

Written by the indexing model from the issue text.