[ash] Don't remove an item when associated window is dragged

ash/shelf/shelf_window_watcher.cc

Index: ash/shelf/shelf_window_watcher.cc
diff --git a/ash/shelf/shelf_window_watcher.cc b/ash/shelf/shelf_window_watcher.cc
index b4e65e25a7b2f50761de5c0c524936e86163917c..c8c9a876aca593a00ccc60fb2c983c5a97552d0b 100644
--- a/ash/shelf/shelf_window_watcher.cc
+++ b/ash/shelf/shelf_window_watcher.cc
@@ -11,6 +11,7 @@
 #include "ash/shelf/shelf_window_watcher_item_delegate.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
+#include "ash/wm/window_state.h"
 #include "ash/wm/window_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/aura/client/activation_client.h"
@@ -40,6 +41,11 @@ bool HasLauncherItemForWindow(aura::Window* window) {
   return false;
 }
 
+// Returns true if |window| is in the process of being dragged.
+bool IsDragging(aura::Window* window) {
+  return ash::wm::GetWindowState(window)->is_dragged();
+}
+
 }  // namespace
 
 namespace ash {
@@ -156,11 +162,12 @@ void ShelfWindowWatcher::OnWindowAdded(aura::Window* window) {
 }
 
 void ShelfWindowWatcher::OnWillRemoveWindow(aura::Window* window) {
-  // Remove a child window of default container and its item if it has.
+  // Remove a child window of default container.
   if (observed_windows_.IsObserving(window))
     observed_windows_.Remove(window);
 
-  if (HasLauncherItemForWindow(window))
+  // When |window| is dragged, its item should not be removed.
+  if (HasLauncherItemForWindow(window) && !IsDragging(window))

[sky, 2013/12/14 00:17:20]

If the window is deleted while dragging how does this cleanup? You remove the
observer on 167, right? Please add test coverage for this.

[simonhong, 2013/12/16 02:24:16]

When a |window| is dragging its observer and item is not removed.
Instead, deleted |window| during the dragging is handled by
OnWindowDestroying().
For the test case, I found that WindowResizer can't handle deleted |window|
during the dragging. WindowResizer uses weak pointer of |window|. So I can't
simulate deleting a |window| before WindowResizer is destroyed for now. I think
it needs some refactoring for this.

     RemoveLauncherItem(window);
 }