Add panels as a single group of windows per display for overview window cycling.

ui/aura/window.cc

Index: ui/aura/window.cc
diff --git a/ui/aura/window.cc b/ui/aura/window.cc
index 6053c0be43970a6441f4ef423f2701389b66812e..f03f352807f13a7b5f67f1a80a406a22677f45d6 100644
--- a/ui/aura/window.cc
+++ b/ui/aura/window.cc
@@ -702,8 +702,12 @@ void Window::SetBoundsInternal(const gfx::Rect& new_bounds) {
 }
 
 void Window::SetVisible(bool visible) {
-  if (visible == layer_->GetTargetVisibility())
+  if (visible == layer_->GetTargetVisibility()) {
+    // After calling SetVisible, IsVisible should immediately return the target
+    // visibility state.

[sky, 2013/09/13 21:46:44]

I think this is wrong. The reason you're seeing the behavior you are is you're
changing the visibility at the layer level directly. You need to go through
window otherwise things get out of sync.

[flackr, 2013/09/13 22:28:38]

I should provide some context. PanelLayoutManager::MinimizePanel it calls
Window::Hide and then in PanelLayoutManager::Relayout expects Window::IsVisible
to return false. Both of these calls are made on the Window and I think should
return a consistent result even though the layer is animating as described in
the comment in Window::IsVisible, but let me know what you think.

[sky, 2013/09/16 17:03:35]

725 updates visibility, so how come PanelLayoutManager is not seeing the correct
visible state?

+    visible_ = visible;
     return;  // No change.
+  }
 
   FOR_EACH_OBSERVER(WindowObserver, observers_,
                     OnWindowVisibilityChanging(this, visible));