Improved Chromebook Support

[tcr]

The demo I ran at RustConf ran on Chromebooks, specifically the Asus Chromebook Flip C302CA (which is also The Wirecutter's recommendation for best Chromebook). These machines were great to demo with, since they synced the browser's starting and home pages, auto-loaded the "never sleep" extension required to keep the demo running, and could be completed cleaned and rebooted in a matter of minutes. Chromebooks differ, and the Asus Flip featured a tablet mode that allowed the keyboard to be swung behind the screen on a 180° hinge. There's a few features that could better accomodate various Chromebook modes:

• Support showing the virtual keyboard by default in tablet mode. The easiest way to trigger this is to give focus to an or <textarea> element, but that implies that the cursor needs to be a "text input" element and not just a
  to make this work cross-platform. The upshot is accessibility APIs can also be tapped into in this way.
• Allow dragging to select a section of text using multitouch. At the moment the caret follows wherever you drag with your finger. It never initializes the "selection" logic to set a starting anchor caret and have the focus caret follow the user. (This may just involve changing out JS events that are mouse-specific events with touch-aware events.)
• Allow edit.io to be installed as a native Chrome App.

cc @creationix

[tcr]

Unrelatedly, I switched to running demos on the Dell Chromebook 3380, an incredibly cheap and yet capable computer which can be purchased from the Dell Refurbishing Outlet for $230. They're perfect rubberized demo machines, and faster than most other low-end Chromebooks.