Improve layout sizing.
Review Request #7251 — Created April 24, 2015 and submitted
The mix of height/width-based divs and flexbox was causing some issues with
scrolling, especially when a student view was visible. These changes make
things fill the screen better.
Made my window small and scrolled around. Saw that everything that was supposed
to be full-bleed was, and that nothing scrolled oddly.
Tool: PEP8 Style Checker Ignored Files: lib/frontend/main.js style.css Tool: Pyflakes Ignored Files: lib/frontend/main.js style.css