Put the previous snapped window in splitview back in overview.

To be consistent with tablet splitview behavior, we decided to do the
same when in overview dragging an overview window to snap to a position
that already has a snapped window in place: the previous snapped window
will be put back into overview.

Bug:991695
TEST: SplitViewOverviewSessionInClamshellTest.BasicFunctionalitiesTest

Change-Id: I3411fff3257146bdcd6b4344206a7bbb1fbd6340
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1765444
Commit-Queue: Xiaoqian Dai <xdai@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#690976}

ash/wm/overview/overview_session_unittest.cc

@@ -4553,7 +4553,7 @@ TEST_F(SplitViewOverviewSessionInClamshellTest, BasicFunctionalitiesTest) {
 
   // 4. Test if one window is snapped, the other windows are showing in
   // overview, we can drag another window in overview to snap in splitview, and
-  // the previous snapped window will not be put back into overview.
+  // the previous snapped window will be put back into overview.
   std::unique_ptr<aura::Window> window4(CreateWindow(bounds));
   ToggleOverview();
   overview_item1 = GetOverviewItemForWindow(window1.get());
@@ -4564,7 +4564,7 @@ TEST_F(SplitViewOverviewSessionInClamshellTest, BasicFunctionalitiesTest) {
   DragWindowTo(overview_item3, gfx::PointF(0, 0));
   EXPECT_FALSE(overview_controller()->overview_session()->IsWindowInOverview(
       window3.get()));
-  EXPECT_FALSE(overview_controller()->overview_session()->IsWindowInOverview(
+  EXPECT_TRUE(overview_controller()->overview_session()->IsWindowInOverview(
       window1.get()));
   EXPECT_EQ(window_state1->GetStateType(), WindowStateType::kLeftSnapped);
   EXPECT_EQ(WindowState::Get(window3.get())->GetStateType(),

ash/wm/splitview/split_view_controller.cc

@@ -382,29 +382,28 @@ void SplitViewController::SnapWindow(aura::Window* window,
   }
   StartObserving(window);
 
-  if (split_view_type_ == SplitViewType::kTabletType) {
-    // Insert the previous snapped window to overview if overview is active.
-    if (previous_snapped_window && GetOverviewSession()) {
-      InsertWindowToOverview(previous_snapped_window);
-      // Ensure that the close icon will fade in. This part is redundant for
-      // dragging from overview, but necessary for dragging from the top. For
-      // dragging from overview, |OverviewItem::OnSelectorItemDragEnded| will be
-      // called on all overview items including the |previous_snapped_window|
-      // item anyway, whereas for dragging from the top,
-      // |OverviewItem::OnSelectorItemDragEnded| already was called on all
-      // overview items and |previous_snapped_window| was not yet among them.
-      GetOverviewSession()
-          ->GetOverviewItemForWindow(previous_snapped_window)
-          ->OnSelectorItemDragEnded(/*snap=*/true);
-    }
+  // Insert the previous snapped window to overview if overview is active.
+  if (previous_snapped_window && GetOverviewSession()) {
+    InsertWindowToOverview(previous_snapped_window);
+    // Ensure that the close icon will fade in. This part is redundant for
+    // dragging from overview, but necessary for dragging from the top. For
+    // dragging from overview, |OverviewItem::OnSelectorItemDragEnded| will be
+    // called on all overview items including the |previous_snapped_window|
+    // item anyway, whereas for dragging from the top,
+    // |OverviewItem::OnSelectorItemDragEnded| already was called on all
+    // overview items and |previous_snapped_window| was not yet among them.
+    GetOverviewSession()
+        ->GetOverviewItemForWindow(previous_snapped_window)
+        ->OnSelectorItemDragEnded(/*snap=*/true);
+  }
 
     // Update the divider position and window bounds before snapping a new
     // window. Since the minimum size of |window| maybe larger than currently
     // bounds in |snap_position|.
-    if (state_ != SplitViewState::kNoSnap) {
-      divider_position_ = GetClosestFixedDividerPosition();
-      UpdateSnappedWindowsAndDividerBounds();
-    }
+  if (state_ != SplitViewState::kNoSnap &&
+      split_view_type_ == SplitViewType::kTabletType) {
+    divider_position_ = GetClosestFixedDividerPosition();
+    UpdateSnappedWindowsAndDividerBounds();
   }
 
   // Disable the bounds change animation for a to-be-snapped window if the