Put the new selector item as the first one in overview grid.

Bug: 872052
Test: SplitViewTabDraggingTest.ShowNewWindowItemWhenDragStarts
Change-Id: Ib7a563d350fb5d789495518b414f7a319bc9063b
Reviewed-on: https://chromium-review.googlesource.com/1168592
Commit-Queue: Min Chen <minch@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581969}

ash/wm/overview/window_grid.cc

@@ -478,9 +478,10 @@ void WindowGrid::AddItem(aura::Window* window, bool reposition, bool animate) {
 
   window_observer_.Add(window);
   window_state_observer_.Add(wm::GetWindowState(window));
-  window_list_.push_back(
+  window_list_.insert(
+      window_list_.begin(),
       std::make_unique<WindowSelectorItem>(window, window_selector_, this));
-  window_list_.back()->PrepareForOverview();
+  window_list_.front()->PrepareForOverview();
 
   if (reposition)
     PositionWindows(animate);

ash/wm/splitview/split_view_controller_unittest.cc

@@ -2216,7 +2216,8 @@ TEST_F(SplitViewTabDraggingTest, ShowNewWindowItemWhenDragStarts) {
   EXPECT_EQ(split_view_controller()->state(),
             SplitViewController::RIGHT_SNAPPED);
 
-  // Test that the new window item widget shows up.
+  // Test that the new window item widget shows up as the first one of the
+  // windows in the grid.
   WindowSelector* window_selector =
       Shell::Get()->window_selector_controller()->window_selector();
   WindowGrid* current_grid =
@@ -2230,6 +2231,7 @@ TEST_F(SplitViewTabDraggingTest, ShowNewWindowItemWhenDragStarts) {
       current_grid->GetWindowSelectorItemContaining(
           new_selector_widget->GetNativeWindow());
   ASSERT_TRUE(new_selector_item);
+  EXPECT_EQ(new_selector_item, current_grid->window_list().front().get());
   const gfx::Rect new_selector_bounds = new_selector_item->target_bounds();
   DragWindowTo(resizer.get(), new_selector_bounds.CenterPoint());
   CompleteDrag(std::move(resizer));
@@ -2237,8 +2239,12 @@ TEST_F(SplitViewTabDraggingTest, ShowNewWindowItemWhenDragStarts) {
   EXPECT_TRUE(Shell::Get()->window_selector_controller()->IsSelecting());
   EXPECT_EQ(split_view_controller()->state(),
             SplitViewController::RIGHT_SNAPPED);
-  // Test that the dragged window has been added to the overview mode.
+  // Test that the dragged window has been added to the overview mode, and it is
+  // added at the front of the grid.
   EXPECT_EQ(current_grid->window_list().size(), 2u);
+  WindowSelectorItem* first_selector_item =
+      current_grid->GetWindowSelectorItemContaining(window1.get());
+  EXPECT_EQ(first_selector_item, current_grid->window_list().front().get());
   EXPECT_TRUE(window_selector->IsWindowInOverview(window1.get()));
   EXPECT_TRUE(window_selector->IsWindowInOverview(window3.get()));
   // Test that the new window item widget has been destroyed.

ash/wm/tablet_mode/tablet_mode_window_drag_delegate.cc

@@ -50,11 +50,12 @@ gfx::Rect GetNewSelectorItemBounds(aura::Window* dragged_window) {
   if (!window_grid || window_grid->empty())
     return gfx::Rect();
 
-  WindowSelectorItem* last_item = window_grid->window_list().back().get();
-  if (!window_grid->IsNewSelectorItemWindow(last_item->GetWindow()))
+  WindowSelectorItem* new_selector_item =
+      window_grid->window_list().front().get();
+  if (!window_grid->IsNewSelectorItemWindow(new_selector_item->GetWindow()))
     return gfx::Rect();
 
-  return last_item->target_bounds();
+  return new_selector_item->target_bounds();
 }
 
 // Set |transform| to |window| and its transient child windows. |transform| is