Plumb maxTouchPoints for AuraX11

Aura implementation for
navigator.maxTouchPoints defined in the W3C Pointer Events
standard draft:
http://www.w3.org/TR/pointerevents/#widl-Navigator-maxTouchPoints

BUG=312926
TEST=navigator.maxTouchPoints shows 16 on Pixel.

Review URL: https://codereview.chromium.org/59903023

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235528 0039d316-1c4b-4281-b951-d872f2087c98
The chrome.screenlockPrivate API allows select apps to control the ChromeOS ScreenLocker.

https://docs.google.com/document/d/1kSxngeyBPZIB7kK-QfDXgpzrDBvnVBcJfbK3HMFQIZg/edit

The live version of the whitelisted app uses the chrome.usb API to execute a challenge-response protocol with an experimental device that has received a provisional green light from Google Security Team for unlocking.

Review URL: https://codereview.chromium.org/60583003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235529 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235529