Improvements to the offline intersitial and easter egg
- Fix right click restart bug.
- Switched image assets to use sprite sheets.
- Fix resizing whilst jumping causes delays bug.
- Add UMA counter for easter egg.
- Gameplay tweaks.

BUG=464330,453853

Review URL: https://codereview.chromium.org/1051433002

Cr-Commit-Position: refs/heads/master@{#323703}
27 files changed