events: Make platform specific events code into ui/events/.

events: Make platform specific events code into ui/events/.

Notable changes:
 * Move events_win and events_x from ui/base/ into ui/events/
 * Move DeviceDataManager, and DeviceListCache into ui/events/
 * Move X11AtomCache from ui/base/x into ui/gfx/x
 * Move some X11 util functions from ui/base/ into ui/events/

BUG=none
R=ben@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=225163

[sadrul, 2013-09-25 03:40:31]

There is still dependency on TouchFactory for X11, and some switches need to be
moved from ui_base_switches into events_switches. With those done, events can be
a new target.

(I am not so sure about events_unittests right now though, since that would
require updating a number of try/build bots too)

[Ben Goodger (Google), 2013-09-25 04:13:26]

lgtm

[sadrul, 2013-09-25 09:15:40]

Committed patchset #1 manually as r225163 (presubmit successful).