Support /dev/{tty,cu}.SLAB* in serial port enumeration

This is a temporary fix to support a large number of USB-serial devices on
OS X.

BUG=230694

Review URL: https://codereview.chromium.org/99103005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238598 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238598
Sticky keys modifies an entire scroll sequence instead of just a single event.

A scroll sequence starts with a fling cancel, followed by a series of scroll
events and ends with a fling start event. In the oneshot sticky keys case, we
now modify the entire sequence with the modifier key before disabling sticky
keys.

Recommitting r236834 because it was reverted due to a memory leak.

BUG=308662
TEST=updated unit tests, ran valgrind test

Review URL: https://codereview.chromium.org/99213003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238599 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238599
[rAC, OSX] Once more rAC for OSX is on by default.

R=estade@chromium.org
BUG=none

Review URL: https://codereview.chromium.org/99473005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238600 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238600