MonitorManager to manage multiple monitors.

MonitorManager to manage multiple monitors.
* Changed related classes (ScreenAura and layout managers) to use MonitorManager to retrieve monitor information. This will be used to show a message window on another monitor in fullscreen.
* SingleMonitorManager for testing. I'll add MonitorManagerX that supports multimonitor under x11.
* ScreenAura's CursorPosition methods are unchanged because this doesn't have to be changed for m19.

BUG=115510
TEST=tbd

[Ben Goodger (Google), 2012-03-13 19:28:12]

http://codereview.chromium.org/9689027/diff/79/ui/aura/monitor.h
File ui/aura/monitor.h (right):

http://codereview.chromium.org/9689027/diff/79/ui/aura/monitor.h#newcode20
ui/aura/monitor.h:20: // Set/gets monitor's bounds in screen's coordinates.
what does it mean to set the monitor's bounds in screen coordinates? screen to
me is a component of a monitor (i.e. my LCD monitor has a plastic screen).

Do you mean global coordinates relative to primary screen?

[oshima, 2012-03-13 20:06:37]

http://codereview.chromium.org/9689027/diff/79/ui/aura/monitor.h
File ui/aura/monitor.h (right):

http://codereview.chromium.org/9689027/diff/79/ui/aura/monitor.h#newcode20
ui/aura/monitor.h:20: // Set/gets monitor's bounds in screen's coordinates.
On 2012/03/13 19:28:12, Ben Goodger (Google) wrote:
> what does it mean to set the monitor's bounds in screen coordinates? screen to
> me is a component of a monitor (i.e. my LCD monitor has a plastic screen).
> 
> Do you mean global coordinates relative to primary screen?

By screen, I meant the coordinate system used by "gfx::Screen", which will be
relative to primary screen on aura, at least for m19. I'll update the comment.

Mac uses the same scheme, but Windows is slightly different
(http://www.flounder.com/virtual_screen_coordinates.htm). 
Xrandr is somewhat similar to Windows I believe. I'm fine with either way, so
let me know if you have preference.

[Ben Goodger (Google), 2012-03-13 20:47:04]

Can you clarify (in the code related to aura::Monitor) what the relationship
between aura::Monitor and gfx::Screen is?

[Ben Goodger (Google), 2012-03-13 21:04:39]

lgtm