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

ash/wm/panels/panel_window_resizer.cc

Index: ash/wm/panels/panel_window_resizer.cc
diff --git a/ash/wm/panels/panel_window_resizer.cc b/ash/wm/panels/panel_window_resizer.cc
index e306f29411bcc3ba85c4bc4ef58639947c21a03c..6b87e201100adc0d89b0a0e5276c08d435b9b2e6 100644
--- a/ash/wm/panels/panel_window_resizer.cc
+++ b/ash/wm/panels/panel_window_resizer.cc
@@ -12,7 +12,10 @@
 #include "ash/shell_window_ids.h"
 #include "ash/wm/panels/panel_layout_manager.h"
 #include "ash/wm/property_util.h"
+#include "ash/wm/toplevel_window_event_handler.h"
 #include "ash/wm/window_properties.h"
+#include "ash/wm/workspace/workspace_event_handler.h"
+#include "ash/wm/workspace_controller.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/env.h"
 #include "ui/aura/root_window.h"
@@ -36,8 +39,8 @@ PanelWindowResizer::~PanelWindowResizer() {
 // static
 PanelWindowResizer*
 PanelWindowResizer::Create(aura::Window* window,
-                             const gfx::Point& location,
-                             int window_component) {
+                           const gfx::Point& location,
+                           int window_component) {
   Details details(window, location, window_component);
   return details.is_resizable ? new PanelWindowResizer(details) : NULL;
 }
@@ -57,7 +60,8 @@ void PanelWindowResizer::Drag(const gfx::Point& location, int event_flags) {
 }
 
 void PanelWindowResizer::CompleteDrag(int event_flags) {
-  if (should_attach_ != was_attached_) {
+  if (details_.window->GetProperty(internal::kPanelAttachedKey) !=
+      should_attach_) {
     details_.window->SetProperty(internal::kPanelAttachedKey, should_attach_);
     details_.window->SetDefaultParentByRootWindow(
             details_.window->GetRootWindow(),
@@ -140,13 +144,28 @@ bool PanelWindowResizer::AttachToLauncher(gfx::Rect* bounds) {
 }
 
 void PanelWindowResizer::StartedDragging() {
-  if (was_attached_)
-    panel_layout_manager_->StartDragging(details_.window);
+  // Tell the panel layout manager that we are dragging this panel before
+  // attaching it so that it does not get repositioned.
+  panel_layout_manager_->StartDragging(details_.window);
+  if (!was_attached_) {
+    ash::internal::RootWindowController* root_window_controller =
+        GetRootWindowController(details_.window->GetRootWindow());
+    // Pass the resize handler from the workspace event handler to the panel
+    // container event handler so it can continue to carry out the drag.
+    root_window_controller->workspace_controller()->GetEventHandlerForWindow(
+        details_.window)->PassResizer(
+            root_window_controller->panel_container_handler());
+
+    // Attach the panel while dragging placing it in front of other panels.
+    details_.window->SetProperty(internal::kPanelAttachedKey, true);
+    details_.window->SetDefaultParentByRootWindow(
+            details_.window->GetRootWindow(),
+            details_.window->bounds());
+  }
 }
 
 void PanelWindowResizer::FinishDragging() {
-  if (was_attached_)
-    panel_layout_manager_->FinishDragging();
+  panel_layout_manager_->FinishDragging();
 }
 
 }  // namespace aura