Move IN_OVERFLOW from Panel::ExpansionState to new enum.

chrome/browser/ui/panels/panel_manager.h

Index: chrome/browser/ui/panels/panel_manager.h
diff --git a/chrome/browser/ui/panels/panel_manager.h b/chrome/browser/ui/panels/panel_manager.h
index 38158137d6811567586431a01c8fc41efab454a4..7a88ffcba6a131cfe05fffdcddb2c433b17db947 100644
--- a/chrome/browser/ui/panels/panel_manager.h
+++ b/chrome/browser/ui/panels/panel_manager.h
@@ -47,8 +47,12 @@ class PanelManager : public AutoHidingDesktopBar::Observer {
   void Drag(int delta_x);
   void EndDragging(bool cancelled);
 
+  // Invoked when a panel's strip owner changes.
+  void OnPanelStripOwnerChanged(Panel* panel, Panel::StripOwner old_owner);
+
   // Invoked when a panel's expansion state changes.
-  void OnPanelExpansionStateChanged(Panel* panel);
+  void OnPanelExpansionStateChanged(Panel* panel,
+                                    Panel::ExpansionState old_state);
 
   // Invoked when a panel is starting/stopping drawing an attention.
   void OnPanelAttentionStateChanged(Panel* panel);