Add persisted preference for projection touch HUD

A new preference is created showing if the projection touch HUD is
enabled or not. This preference is per-user and unsyncable. It is not
exposed anywhere in the UI, but can be toggled using the Ctrl+Alt+9
accelerator combination.

BUG=233567

Review URL: https://chromiumcodereview.appspot.com/18163006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@210516 0039d316-1c4b-4281-b951-d872f2087c98
8 files changed