Move focus from the view manager to the window manager.

Move focus from the view manager to the window manager.

Focus and activation are closely related. Focus could
perhaps be considered a view manager concept, but
activation is window-manager specific, and cannot. Event
dispatch is influenced by (among other things) focus. So,
move event dispatch to the window manager.

I still like the idea of the view manager client lib
providing a "flattened" API to users that allows
setting/querying focus state & observing changes, rather
than obliging everyone connect to the window manager
independently (though they may want to do so for other
reasons). So I'm having the view manager client connect
to the window manager & continue to provide the
SetFocus()/FocusChanged APIs. This causes a minor dilemma
in that we have two window managers but only one view
manager client. Right now I resolved this by defaulting
to the original window manager and allowing others to be
specified on the command line to the shell, but I think
we will eventually want a way to register a default
window manager.

R=sky@chromium.org
BUG=

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=289975

[sky, 2014-08-15 18:03:56]

LGTM

https://codereview.chromium.org/474883003/diff/200001/mojo/examples/window_ma...
File mojo/examples/window_manager/window_manager.cc (right):

https://codereview.chromium.org/474883003/diff/200001/mojo/examples/window_ma...
mojo/examples/window_manager/window_manager.cc:366:
window_manager_app_->host()->window()->AddPreTargetHandler(this);
Do you need to remove the pre target handler at some point?

https://codereview.chromium.org/474883003/diff/200001/mojo/services/view_mana...
File mojo/services/view_manager/node_delegate.h (right):

https://codereview.chromium.org/474883003/diff/200001/mojo/services/view_mana...
mojo/services/view_manager/node_delegate.h:11: class Event;
You can remove this now.

https://codereview.chromium.org/474883003/diff/200001/mojo/services/window_ma...
File mojo/services/window_manager/window_manager_app.cc (right):

https://codereview.chromium.org/474883003/diff/200001/mojo/services/window_ma...
mojo/services/window_manager/window_manager_app.cc:349:
window->AddPreTargetHandler(this);
RemovePreTargetHandler in destructor?

[Ben Goodger (Google), 2014-08-15 19:28:16]

Committed patchset #12 manually as 289975 (presubmit successful).