Makes MouseWatcher work while in metro mode

Makes MouseWatcher work while in metro mode

I'm changing the aura implementation to use
Env::AddPreTargetListener. This way I don't need MessageLoop specific
code and it'll work correctly for win on both metro and non-metro.

BUG=315155
TEST=none
R=ben@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=233270

[sky, 2013-11-05 18:52:56]

https://codereview.chromium.org/60443003/diff/1/ui/views/mouse_watcher.cc
File ui/views/mouse_watcher.cc (right):

https://codereview.chromium.org/60443003/diff/1/ui/views/mouse_watcher.cc#new...
ui/views/mouse_watcher.cc:29: #if defined(OS_WIN) && !defined(USE_AURA)
I'm going with totally different ifdefs since hopefully soon we can nuke all the
non-aura code.

[Ben Goodger (Google), 2013-11-05 19:07:10]

lgtm

[commit-bot: I haz the power, 2013-11-05 19:13:45]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/sky@chromium.org/60443003/1

[commit-bot: I haz the power, 2013-11-05 23:31:08]

Retried try job too often on linux_aura for step(s) browser_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=linux_aura...

[commit-bot: I haz the power, 2013-11-05 23:56:35]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/sky@chromium.org/60443003/1

[commit-bot: I haz the power, 2013-11-06 03:41:55]

Retried try job too often on linux_aura for step(s) browser_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=linux_aura...

[sky, 2013-11-06 14:34:02]

Committed patchset #1 manually as r233270 (presubmit successful).