Prevents panels attached to shelf from docking

ash/wm/dock/docked_window_layout_manager.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/wm/dock/docked_window_layout_manager.h"
 
 #include "ash/ash_switches.h"
 #include "ash/screen_ash.h"
 #include "ash/shelf/shelf.h"
 #include "ash/shelf/shelf_constants.h"
@@ skipping 514 matching lines @@
   // No docked windows remain other than possibly the window being dragged.
   // Return |NONE| to indicate that windows may get docked on either side.
   return DOCKED_ALIGNMENT_NONE;
 }
 
 bool DockedWindowLayoutManager::CanDockWindow(aura::Window* window,
                                               SnapType edge) {
   if (!switches::UseDockedWindows())
     return false;
   // Don't allow interactive docking of windows with transient parents such as
-  // modal browser dialogs.
-  if (IsPopupOrTransient(window))
+  // modal browser dialogs. Prevent docking of panels attached to shelf during
+  // the drag.
+  wm::WindowState* window_state = wm::GetWindowState(window);
+  bool should_attach_to_shelf = window_state->drag_details() &&
+      window_state->drag_details()->should_attach_to_shelf;
+  if (IsPopupOrTransient(window) || should_attach_to_shelf)
     return false;
   // If a window is wide and cannot be resized down to maximum width allowed
   // then it cannot be docked.
   // TODO(varkha). Prevent windows from changing size programmatically while
   // they are docked. The size will take effect only once a window is undocked.
   // See http://crbug.com/307792.
   if (window->bounds().width() > kMaxDockWidth &&
-      (!wm::GetWindowState(window)->CanResize() ||
+      (!window_state->CanResize() ||
        (window->delegate() &&
         window->delegate()->GetMinimumSize().width() != 0 &&
         window->delegate()->GetMinimumSize().width() > kMaxDockWidth))) {
     return false;
   }
   // If a window is tall and cannot be resized down to maximum height allowed
   // then it cannot be docked.
   const gfx::Rect work_area =
       Shell::GetScreen()->GetDisplayNearestWindow(dock_container_).work_area();
   if (GetWindowHeightCloseTo(window, work_area.height()) > work_area.height())
@@ skipping 688 matching lines @@
 void DockedWindowLayoutManager::OnKeyboardBoundsChanging(
     const gfx::Rect& keyboard_bounds) {
   // This bounds change will have caused a change to the Shelf which does not
   // propagate automatically to this class, so manually recalculate bounds.
   Relayout();
   UpdateDockBounds(DockedWindowLayoutManagerObserver::KEYBOARD_BOUNDS_CHANGING);
 }
 
 }  // namespace internal
 }  // namespace ash