Add touch scrolling modes experimental flags

In particular, adds --touch-scrolling-mode=absorb-touchmove,
and --touch-scrolling-mode=sync-touchmove.

Split out of https://codereview.chromium.org/156783006, which was migrated from https://codereview.chromium.org/140253005/ so some review history is there.

BUG=328503
TEST=TouchEventQueueTest.SyncTouchMoveDoesntCancelTouchOnScroll,
  TouchEventQueueTest.TouchAbsorption

Review URL: https://codereview.chromium.org/166923002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251596 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251596
Exposed virtual keyboard control in kiosk mode.

BUG=343670
TEST=expanded ExtensionApiTest.ChromeOSInfoPrivateTest

Review URL: https://codereview.chromium.org/164993003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251597 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251597
Blink roll 167235:167241

http://build.chromium.org/f/chromium/perf/dashboard/ui/changelog_blink.html?url=/trunk&range=167236:167241&mode=html
TBR=
BUG=

Review URL: https://codereview.chromium.org/166293003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251598 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251599 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251599
Support all 8 dots for braille keyboard input.

Add tests for all keyboard commands currently recognized.

BUG=310285
R=dtseng@chromium.org

Review URL: https://codereview.chromium.org/145813008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251600 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251600