Dragging panels near screen edge

ash/wm/panels/panel_layout_manager.cc

Index: ash/wm/panels/panel_layout_manager.cc
diff --git a/ash/wm/panels/panel_layout_manager.cc b/ash/wm/panels/panel_layout_manager.cc
index c4ccd11a3d878a0cd6728166abfa487147f3bfeb..d2acef858a6ddcb338c7b153566621b0ceae8232 100644
--- a/ash/wm/panels/panel_layout_manager.cc
+++ b/ash/wm/panels/panel_layout_manager.cc
@@ -13,9 +13,11 @@
 #include "ash/shelf/shelf_types.h"
 #include "ash/shelf/shelf_widget.h"
 #include "ash/shell.h"
+#include "ash/shell_window_ids.h"
 #include "ash/wm/frame_painter.h"
 #include "ash/wm/property_util.h"
 #include "ash/wm/window_animations.h"
+#include "ash/wm/window_properties.h"
 #include "ash/wm/window_util.h"
 #include "base/auto_reset.h"
 #include "base/bind.h"
@@ -328,6 +330,19 @@ void PanelLayoutManager::OnWindowResized() {
 void PanelLayoutManager::OnWindowAddedToLayout(aura::Window* child) {
   if (child->type() == aura::client::WINDOW_TYPE_POPUP)
     return;
+  if (!child->GetProperty(kPanelAttachedKey)) {
+    // This should only happen when a window is added to panel container as a
+    // result of bounds change from within the application during a drag.
+    // If so we have already stopped the drag and should reparent the panel
+    // back to appropriate container and ignore it.
+    // TODO(varkha): Updating bounds during a drag can cause problems and a more
+    // general solution is needed. See http://crbug.com/251813 .
+    child->SetDefaultParentByRootWindow(

[flackr, 2013/06/21 01:14:48]

It makes me uncomfortable that this could cause an infinite recursion if the
default parent was for some reason the panel container. You should probably
guard against that similar to how Relayout prevents infinite recursion.

[varkha, 2013/06/21 01:27:08]

Done. Cannot really happen with our current logic that depends on the same
variable but I am all for additional safeguards.

+        child->GetRootWindow(),
+        child->GetRootWindow()->GetBoundsInScreen());
+    DCHECK(child->parent()->id() != kShellWindowId_PanelContainer);
+    return;
+  }
   PanelInfo panel_info;
   panel_info.window = child;
   panel_info.callout_widget = new PanelCalloutWidget(panel_container_);