mash: Convert FocusCycler to wm common types and move to //ash/common

ash/common/wm_window.h

Index: ash/common/wm_window.h
diff --git a/ash/common/wm_window.h b/ash/common/wm_window.h
index 14cec7f071a882ee2c96880060fc7587af2a2c1f..691a7d770fcfbd550969396fcc9b2c97fce99956 100644
--- a/ash/common/wm_window.h
+++ b/ash/common/wm_window.h
@@ -31,6 +31,10 @@ namespace ui {
 class Layer;
 }
 
+namespace views {
+class Widget;
+}
+
 namespace ash {
 
 class WmLayoutManager;
@@ -203,6 +207,11 @@ class ASH_EXPORT WmWindow {
   virtual void Hide() = 0;
   virtual void Show() = 0;
 
+  // Returns the widget associated with this window, or null if not associated
+  // with a widget. Only ash system UI widgets are returned, not widgets created
+  // by the mus window manager code to show a non-client frame.
+  virtual views::Widget* GetWidget() = 0;

[msw, 2016/06/16 23:57:44]

Hmm, Scott may have some advice here; but I guess it seems okay to me.
(I wonder if it would be helpful to return the mus wm frame widget...)

[sky, 2016/06/17 00:08:29]

I'm ok with this, but I recommend a clearer name. WmWindowMus calls this type of
widget 'internal'. GetInternalWidget? If we need this to return either type,
then GetWidget() is fine.

[James Cook, 2016/06/17 03:39:29]

I only need the internal widget, so I went with GetInternalWidget().

+
   // Requests the window to close and destroy itself. This is intended to
   // forward to an associated widget.
   virtual void CloseWidget() = 0;