Revert "ash: Keep active window uncovered on display change"

This reverts commit 92ecc62f.

Reason for revert: suspect ash_unittests failure on Linux Chromium OS ASan LSan Tests
https://ci.chromium.org/p/chromium/builders/ci/Linux%20Chromium%20OS%20ASan%20LSan%20Tests%20%281%29/32865
ExtendedDesktopTest.KeyEventsOnLockScreen
OverviewSessionTest.RemoveDisplay
OverviewSessionTest.RemoveDisplayWithAnimation
PersistentWindowControllerTest.DisconnectDisplay
PersistentWindowControllerTest.MixedMirrorMode
PersistentWindowControllerTest.NormalMirrorMode
PersistentWindowControllerTest.ReconnectOnLockScreen
PersistentWindowControllerTest.RecordNumOfWindowsRestored
PersistentWindowControllerTest.ThreeDisplays
PersistentWindowControllerTest.WindowMovedByAccel
...

https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket.appspot.com/8915703982173055536/+/steps/ash_unittests/0/logs/Deterministic_failure:_ExtendedDesktopTest.KeyEventsOnLockScreen__status_CRASH_/0
==31193==ERROR: AddressSanitizer: container-overflow on address 0x6020001da810 at pc 0x55d92be6ea70 bp 0x7ffe03af0a30 sp 0x7ffe03af0a28
READ of size 8 at 0x6020001da810 thread T0
    #0 0x55d92be6ea6f in ReparentAllWindows ./../../ash/root_window_controller.cc:256:41
    #1 0x55d92be6ea6f in ash::RootWindowController::MoveWindowsTo(aura::Window*) ./../../ash/root_window_controller.cc:622:0
    #2 0x55d92bc99cf5 in ash::WindowTreeHostManager::DeleteHost(ash::AshWindowTreeHost*) ./../../ash/display/window_tree_host_manager.cc:563:15

Original change's description:
> ash: Keep active window uncovered on display change
> 
> - FocusActivationStore uses ActivateWindow(nullptr) for deactivating
>   to avoid an arbitrary window covering the active window before
>   Restore().
> - RootWindowController puts the moved windows under existing ones
>   on display change.
> 
> Bug: 945754
> Change-Id: I3cacfd3427b8c98c9ce9dd2da05977120c1c1d65
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1574824
> Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
> Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#652678}

TBR=xiyuan@chromium.org,oshima@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 945754
Change-Id: Ibf3b8cb823388837f6b3d3052e8258b78fd9a9b7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1577223Reviewed-by: Takashi Sakamoto <tasak@google.com>
Commit-Queue: Takashi Sakamoto <tasak@google.com>
Cr-Commit-Position: refs/heads/master@{#652818}

ash/display/window_tree_host_manager.cc

@@ -160,15 +160,12 @@ class FocusActivationStore {
     if (active_ && focused_ != active_)
       tracker_.Add(active_);
 
-    // Deactivate the window to close menu / bubble windows. Deactivating by
-    // setting active window to nullptr to avoid side effects of activating an
-    // arbitrary window, such as covering |active_| before Restore().
-    if (clear_focus && active_)
-      activation_client_->ActivateWindow(nullptr);
+    // Deactivate the window to close menu / bubble windows.
+    if (clear_focus)
+      activation_client_->DeactivateWindow(active_);
 
     // Release capture if any.
     capture_client_->SetCapture(nullptr);
-
     // Clear the focused window if any. This is necessary because a
     // window may be deleted when losing focus (fullscreen flash for
     // example).  If the focused window is still alive after move, it'll

ash/root_window_controller.cc

@@ -244,16 +244,15 @@ void ReparentAllWindows(aura::Window* src, aura::Window* dst) {
       // may change as a result of moving other windows.
       const aura::Window::Windows& src_container_children =
           src_container->children();
-      auto iter = src_container_children.rbegin();
-      while (iter != src_container_children.rend() &&
+      auto iter = src_container_children.begin();
+      while (iter != src_container_children.end() &&
              SystemModalContainerLayoutManager::IsModalBackground(*iter)) {
         ++iter;
       }
       // If the entire window list is modal background windows then stop.
-      if (iter == src_container_children.rend())
+      if (iter == src_container_children.end())
         break;
       ReparentWindow(*iter, dst_container);
-      dst_container->StackChildAtBottom(*iter);
     }
   }
 }

ash/root_window_controller_unittest.cc

@@ -348,50 +348,6 @@ TEST_F(RootWindowControllerTest, MoveWindows_LockWindowsInUnified) {
   EXPECT_EQ("0,0 600x500", lock_screen->GetNativeWindow()->bounds().ToString());
 }
 
-// Tests that the moved windows (except the active one) are put under existing
-// ones.
-TEST_F(RootWindowControllerTest, MoveWindows_UnderExisting) {
-  UpdateDisplay("600x600,300x300");
-
-  display::Screen* screen = display::Screen::GetScreen();
-  const display::Display primary_display = screen->GetPrimaryDisplay();
-  const display::Display secondary_display = GetSecondaryDisplay();
-
-  views::Widget* existing = CreateTestWidget(gfx::Rect(0, 10, 100, 100));
-  ASSERT_EQ(primary_display.id(),
-            screen->GetDisplayNearestWindow(existing->GetNativeWindow()).id());
-
-  views::Widget* moved = CreateTestWidget(gfx::Rect(650, 10, 100, 100));
-  ASSERT_EQ(secondary_display.id(),
-            screen->GetDisplayNearestWindow(moved->GetNativeWindow()).id());
-
-  views::Widget* active = CreateTestWidget(gfx::Rect(650, 10, 100, 100));
-  ASSERT_TRUE(active->IsActive());
-  ASSERT_EQ(secondary_display.id(),
-            screen->GetDisplayNearestWindow(active->GetNativeWindow()).id());
-
-  // Switch to single display.
-  UpdateDisplay("600x500");
-
-  // |active| is still active.
-  ASSERT_TRUE(active->IsActive());
-
-  // |moved| should be put under |existing|.
-  ASSERT_EQ(moved->GetNativeWindow()->parent(),
-            existing->GetNativeWindow()->parent());
-  bool found_existing = false;
-  bool found_moved = false;
-  for (auto* child : moved->GetNativeWindow()->parent()->children()) {
-    if (child == existing->GetNativeWindow())
-      found_existing = true;
-    if (child == moved->GetNativeWindow()) {
-      found_moved = true;
-      break;
-    }
-  }
-  EXPECT_TRUE(found_moved && !found_existing);
-}
-
 TEST_F(RootWindowControllerTest, ModalContainer) {
   UpdateDisplay("600x600");
   RootWindowController* controller = Shell::GetPrimaryRootWindowController();

ash/wm/overview/overview_session.cc

@@ -652,14 +652,8 @@ void OverviewSession::OnWindowActivating(
     ::wm::ActivationChangeObserver::ActivationReason reason,
     aura::Window* gained_active,
     aura::Window* lost_active) {
-  if (ignore_activations_ || gained_active == GetOverviewFocusWindow())
-    return;
-
-  if (!gained_active) {
-    // Cancel overview session and do not restore focus when active window is
-    // set to nullptr. This happens when removing a display.
-    ResetFocusRestoreWindow(false);
-    CancelSelection();
+  if (ignore_activations_ || !gained_active ||
+      gained_active == GetOverviewFocusWindow()) {
     return;
   }