Keep the dragged window at top during drag.

Bug: 862308
Change-Id: I2f018ab228eaee5ca3bcbdd9a318d71f05612ca3
Reviewed-on: https://chromium-review.googlesource.com/1164564Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Min Chen <minch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581270}

ash/wm/overview/scoped_transform_overview_window.cc

@@ -595,7 +595,7 @@ void ScopedTransformOverviewWindow::CreateAndApplyMaskAndShadow() {
   // Add the mask which gives the window selector items rounded corners, and add
   // the shadow around the window.
   ui::Layer* layer = minimized_widget_
-                         ? minimized_widget_->GetContentsView()->layer()
+                         ? minimized_widget_->GetNativeWindow()->layer()
                          : window_->layer();
 
   if (!minimized_widget_)

ash/wm/overview/window_grid.cc

@@ -198,10 +198,6 @@ std::unique_ptr<views::Widget> CreateNewSelectorItemWidget(
   widget->SetContentsView(new NewSelectorItemView());
   widget->Show();
 
-  // Stack the newly created widget below the dragged window.
-  dragged_window->parent()->StackChildBelow(widget->GetNativeWindow(),
-                                            dragged_window);
-
   if (animate) {
     widget->SetOpacity(0.f);
     ui::ScopedLayerAnimationSettings animation_settings(
@@ -577,6 +573,9 @@ void WindowGrid::OnWindowDragStarted(aura::Window* dragged_window,
   window_selector_->AddItem(new_selector_item_widget_->GetNativeWindow(),
                             /*reposition=*/true, animate);
 
+  // Stack the |dragged_window| at top during drag.
+  dragged_window->parent()->StackChildAtTop(dragged_window);
+
   // Called to set caption and title visibility during dragging.
   OnSelectorItemDragStarted(/*item=*/nullptr);
 }

ash/wm/overview/window_grid.h

@@ -124,8 +124,8 @@ class ASH_EXPORT WindowGrid : public aura::WindowObserver,
   void OnSelectorItemDragStarted(WindowSelectorItem* item);
   void OnSelectorItemDragEnded();
 
-  // Called when a window's tab(s) start/continue/end being dragged around in
-  // WindowGrid.
+  // Called when a window (either it's browser window or an app window)
+  // start/continue/end being dragged in tablet mode.
   void OnWindowDragStarted(aura::Window* dragged_window, bool animate);
   void OnWindowDragContinued(aura::Window* dragged_window,
                              const gfx::Point& location_in_screen,

ash/wm/overview/window_selector.h

@@ -139,8 +139,8 @@ class ASH_EXPORT WindowSelector : public display::DisplayObserver,
   void ActivateDraggedWindow();
   void ResetDraggedWindowGesture();
 
-  // Called when a window's tab(s) start/continue/end being dragged around if
-  // overview mode is active.
+  // Called when a window (either it's browser window or an app window)
+  // start/continue/end being dragged in tablet mode.
   // TODO(xdai): Currently it doesn't work for multi-display scenario.
   void OnWindowDragStarted(aura::Window* dragged_window, bool animate);
   void OnWindowDragContinued(aura::Window* dragged_window,