Attach panel while dragging to bring it in front of other panels.

ash/wm/panels/panel_window_resizer.h

Index: ash/wm/panels/panel_window_resizer.h
diff --git a/ash/wm/panels/panel_window_resizer.h b/ash/wm/panels/panel_window_resizer.h
index 76657d3e9839203dd173ffd39e51804007d38d56..044ea66dfa7622fcdfcfb581f8781b2e2236868b 100644
--- a/ash/wm/panels/panel_window_resizer.h
+++ b/ash/wm/panels/panel_window_resizer.h
@@ -14,6 +14,8 @@ class Rect;
 
 namespace ash {
 
+class WindowResizerOwner;
+
 namespace internal {
 class PanelLayoutManager;
 }
@@ -27,7 +29,8 @@ class ASH_EXPORT PanelWindowResizer : public WindowResizer {
 
   // Creates a new PanelWindowResizer. The caller takes ownership of the
   // returned object. Returns NULL if not resizable.
-  static PanelWindowResizer* Create(aura::Window* window,
+  static PanelWindowResizer* Create(WindowResizerOwner* owner,
+                                    aura::Window* window,
                                     const gfx::Point& location,
                                     int window_component);
 
@@ -49,7 +52,8 @@ class ASH_EXPORT PanelWindowResizer : public WindowResizer {
   }
 
  private:
-  explicit PanelWindowResizer(const Details& details);
+  explicit PanelWindowResizer(WindowResizerOwner* owner,
+                              const Details& details);
 
   // Checks if the provided window bounds should attach to the launcher. If true
   // the bounds are modified to snap the window to the launcher.
@@ -63,6 +67,9 @@ class ASH_EXPORT PanelWindowResizer : public WindowResizer {
   // of the drag start.
   void FinishDragging();
 
+  // The owner of this resizer.
+  WindowResizerOwner* owner_;
+
   const Details details_;
 
   // Panel container window.