Support dragging panels to stack and snap.

chrome/browser/ui/panels/detached_panel_collection.cc

Index: chrome/browser/ui/panels/detached_panel_collection.cc
diff --git a/chrome/browser/ui/panels/detached_panel_collection.cc b/chrome/browser/ui/panels/detached_panel_collection.cc
index 94de21c7792faf091f672f39324715fd0b44ebc3..69d972acf39d0c7117d821cdad5ee89769dac5fd 100644
--- a/chrome/browser/ui/panels/detached_panel_collection.cc
+++ b/chrome/browser/ui/panels/detached_panel_collection.cc
@@ -205,6 +205,7 @@ void DetachedPanelCollection::UpdatePanelOnCollectionChange(Panel* panel) {
   panel->SetAlwaysOnTop(false);
   panel->EnableResizeByMouse(true);
   panel->UpdateMinimizeRestoreButtonVisibility();

[Dmitry Titov, 2013/01/10 00:16:24]

This is where I would add a new method on Panel,
UpdateOnCollectionChange(new_collection_type) and put both calls to
UpdateMinimizeRestoreButtonVisibility() and UpdateStackingProperty() in it.
Otherwise we'll end up calling the same pack of Update...() methods from every
Collection... 
Also, I'd call it from the same place that calls
PanelColelction::UpdatePanelOnColelctionChange().

[jianli, 2013/01/10 02:05:37]

Changed to adding new method OnCollectionChanged() as suggested.

+  panel->UpdateStackingProperty();
 }
 
 void DetachedPanelCollection::OnPanelActiveStateChanged(Panel* panel) {