Prepare status area to support multiple trays.

Prepare status area to support multiple trays. 
* Moves system tray ownership and creation to status area widget.
* Status area is laid out as a grid for support of additional trays.
* Shelf alignment property is moved to TrayBackgroundView

BUG=124914
TEST=Status area tests and functionality should be unaffected.
TBR=ben@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=141671

[stevenjb, 2012-06-11 20:47:01]

This is a subset of http://codereview.chromium.org/10514008/.

Mostly it moves ownership of the system tray to the status area, so that when
the web notification tray is added, shell is not affected and coordinating
visibility (e.g. of notifications) can be handled in StatusAreaWidget.

http://codereview.chromium.org/10535112/diff/2015/ash/shell/content_client/sh...
File ash/shell/content_client/shell_browser_main_parts.cc (right):

http://codereview.chromium.org/10535112/diff/2015/ash/shell/content_client/sh...
ash/shell/content_client/shell_browser_main_parts.cc:83:
chromeos::DBusThreadManager::Initialize();
Needed for TraySms. Was causing ash_shell to crash when run with --ash-notify.

[jennyz, 2012-06-11 23:50:03]

LGTM with:
* Status area is laid out as a grid for support of additional trays.
* Shelf alignment property is moved to TrayBackgroundView

[sadrul, 2012-06-12 15:13:39]

Nice! LGTM with a couple of nits

http://codereview.chromium.org/10535112/diff/2015/ash/shell.h
File ash/shell.h (right):

http://codereview.chromium.org/10535112/diff/2015/ash/shell.h#newcode315
ash/shell.h:315: SystemTray* system_tray();
I feel like it's reasonable to make these accessible from Shell

http://codereview.chromium.org/10535112/diff/2015/ash/system/status_area_widg...
File ash/system/status_area_widget.h (right):

http://codereview.chromium.org/10535112/diff/2015/ash/system/status_area_widg...
ash/system/status_area_widget.h:24: public:
+space

http://codereview.chromium.org/10535112/diff/2015/ash/system/status_area_widg...
ash/system/status_area_widget.h:46: // Child views owned by the view hierarchy:
This comment is probably misplaced? (or needs some rewording to clarify :) )

http://codereview.chromium.org/10535112/diff/2015/ash/system/status_area_widg...
File ash/system/status_area_widget_delegate.cc (right):

http://codereview.chromium.org/10535112/diff/2015/ash/system/status_area_widg...
ash/system/status_area_widget_delegate.cc:85: // so that the widget gets laid
out correctly when tray sizes change.
I am not entirely sure we need grid-layout for this. (SystemTray resizes when
items change size/visibility, and it doesn't use this)

[stevenjb, 2012-06-12 16:46:50]

http://codereview.chromium.org/10535112/diff/2015/ash/shell.h
File ash/shell.h (right):

http://codereview.chromium.org/10535112/diff/2015/ash/shell.h#newcode315
ash/shell.h:315: SystemTray* system_tray();
On 2012/06/12 15:13:39, sadrul wrote:
> I feel like it's reasonable to make these accessible from Shell

TODO removed (for now anyway). I'd kind of prefer to move all access through
status area, but we'll see how that looks.

http://codereview.chromium.org/10535112/diff/2015/ash/system/status_area_widg...
File ash/system/status_area_widget.h (right):

http://codereview.chromium.org/10535112/diff/2015/ash/system/status_area_widg...
ash/system/status_area_widget.h:24: public:
On 2012/06/12 15:13:39, sadrul wrote:
> +space

Done.

http://codereview.chromium.org/10535112/diff/2015/ash/system/status_area_widg...
ash/system/status_area_widget.h:46: // Child views owned by the view hierarchy:
On 2012/06/12 15:13:39, sadrul wrote:
> This comment is probably misplaced? (or needs some rewording to clarify :) )
Clarified, hopefully :)

http://codereview.chromium.org/10535112/diff/2015/ash/system/status_area_widg...
File ash/system/status_area_widget_delegate.cc (right):

http://codereview.chromium.org/10535112/diff/2015/ash/system/status_area_widg...
ash/system/status_area_widget_delegate.cc:85: // so that the widget gets laid
out correctly when tray sizes change.
On 2012/06/12 15:13:39, sadrul wrote:
> I am not entirely sure we need grid-layout for this. (SystemTray resizes when
> items change size/visibility, and it doesn't use this)
I started with BoxLayout. The problem is that then any spacing or alignment has
to be done by each child (i.e. tray), whereas with GridLayout we can specify
padding columns to define the spacing between trays and can center each child
vertically.