Move the panel to the root window where the mouse click occurred.

ash/launcher/launcher_util.cc

Index: ash/launcher/launcher_util.cc
diff --git a/ash/launcher/launcher_util.cc b/ash/launcher/launcher_util.cc
index f7ba77f0bfc2f54263a3c9d571358d5e9de95528..f41ac7dce2932ad183cc3c89e6783e73950b0ddc 100644
--- a/ash/launcher/launcher_util.cc
+++ b/ash/launcher/launcher_util.cc
@@ -6,6 +6,11 @@
 
 #include "ash/launcher/launcher_model.h"
 #include "ash/launcher/launcher_types.h"
+#include "ash/shell.h"
+#include "ui/aura/client/window_types.h"
+#include "ui/aura/window.h"
+#include "ui/views/view.h"
+#include "ui/views/widget/widget.h"
 
 namespace ash {
 namespace launcher {
@@ -18,5 +23,20 @@ int GetBrowserItemIndex(const LauncherModel& launcher_model) {
   return -1;
 }
 
+void MoveToEventRootIfPanel(aura::Window* maybe_panel,
+                            const ui::Event& event) {
+  if (maybe_panel->type() != aura::client::WINDOW_TYPE_PANEL)
+    return;
+  views::View* target = static_cast<views::View*>(event.target());
+  aura::RootWindow* target_root =
+      target ? target->GetWidget()->GetNativeView()->GetRootWindow() : NULL;
+  if (target_root && target_root != maybe_panel->GetRootWindow()) {
+    aura::Window* panel_container =
+        ash::Shell::GetContainer(target_root, maybe_panel->parent()->id());
+    // Move the panel to the target launcher.
+    panel_container->AddChild(maybe_panel);
+  }
+}
+
 }  // namespace launcher
 }  // namespace ash