split view: Adjust init/shutdown order for multi-display split view

In preparation for RootWindowController to own a SplitViewController,
the present CL arranges for the objects to be created at about the same
time, and destroyed at about the same time.

Bug: 970013
Change-Id: I0bcb60c76055124521dd3a33c4a06a299e9ccf0c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1811639
Commit-Queue: Avery Musbach <amusbach@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#698631}

ash/shell.cc

@@ -493,11 +493,6 @@ void Shell::UpdateAfterLoginStatusChange(LoginStatus status) {
     root_window_controller->UpdateAfterLoginStatusChange(status);
 }
 
-void Shell::NotifySplitViewModeStarting() {
-  for (auto& observer : shell_observers_)
-    observer.OnSplitViewModeStarting();
-}
-
 void Shell::NotifySplitViewModeStarted() {
   for (auto& observer : shell_observers_)
     observer.OnSplitViewModeStarted();
@@ -705,10 +700,6 @@ Shell::~Shell() {
   window_cycle_controller_.reset();
   overview_controller_.reset();
 
-  // |split_view_controller_| needs to be deleted after
-  // |overview_controller_|.
-  split_view_controller_.reset();
-
   // Stop dispatching events (e.g. synthesized mouse exits from window close).
   // https://crbug.com/874156
   for (RootWindowController* rwc : GetAllRootWindowControllers())
@@ -795,6 +786,10 @@ Shell::~Shell() {
   // destruction of its owned RootWindowControllers relies on the value.
   window_tree_host_manager_->Shutdown();
 
+  // Destroy |SplitViewController| and |RootWindowController| at about the same
+  // time, as we plan for |RootWindowController| to own a |SplitViewController|.
+  // TODO(crbug.com/970013): Actually carry out that plan.
+  split_view_controller_.reset();
   // Depends on |focus_controller_|, so must be destroyed before.
   window_tree_host_manager_.reset();
 
@@ -1119,6 +1114,10 @@ void Shell::Init(
   system_notification_controller_ =
       std::make_unique<SystemNotificationController>();
 
+  // Create |SplitViewController| and |RootWindowController| at about the same
+  // time, as we plan for |RootWindowController| to own a |SplitViewController|.
+  // TODO(crbug.com/970013): Actually carry out that plan.
+  split_view_controller_ = std::make_unique<SplitViewController>();
   window_tree_host_manager_->InitHosts();
 
   // Create virtual keyboard after WindowTreeHostManager::InitHosts() since
@@ -1147,7 +1146,6 @@ void Shell::Init(
       std::make_unique<ScreenOrientationController>();
   screen_layout_observer_.reset(new ScreenLayoutObserver());
   sms_observer_.reset(new SmsObserver());
-  split_view_controller_.reset(new SplitViewController());
   snap_controller_ = std::make_unique<SnapControllerImpl>();
   key_accessibility_enabler_ = std::make_unique<KeyAccessibilityEnabler>();
 

ash/shell.h

@@ -541,10 +541,6 @@ class ASH_EXPORT Shell : public SessionObserver,
   // TODO(oshima): Investigate if we can merge this and |OnLoginStateChanged|.
   void UpdateAfterLoginStatusChange(LoginStatus status);
 
-  // Notifies observers that split view mode is about to be started (before the
-  // window gets snapped and activated).
-  void NotifySplitViewModeStarting();
-
   // Notifies observers that split view mode has been started.
   void NotifySplitViewModeStarted();
 

ash/shell_observer.h

@@ -41,10 +41,6 @@ class ASH_EXPORT ShellObserver {
   // Invoked when |pinned_window| enter or exit pinned mode.
   virtual void OnPinnedStateChanged(aura::Window* pinned_window) {}
 
-  // Called when the split view mode is about to be started before the window
-  // gets snapped and activated).
-  virtual void OnSplitViewModeStarting() {}
-
   // Called when the split view mode has been started.
   virtual void OnSplitViewModeStarted() {}
 

ash/wm/splitview/split_view_controller.cc

@@ -284,7 +284,6 @@ SplitViewController::SplitViewController() {
 
 SplitViewController::~SplitViewController() {
   display::Screen::GetScreen()->RemoveObserver(this);
-  Shell::Get()->accessibility_controller()->RemoveObserver(this);
   EndSplitView();
 }
 
@@ -325,7 +324,6 @@ void SplitViewController::SnapWindow(aura::Window* window,
     Shell::Get()->AddShellObserver(this);
     Shell::Get()->overview_controller()->AddObserver(this);
     Shell::Get()->activation_client()->AddObserver(this);
-    Shell::Get()->NotifySplitViewModeStarting();
 
     // If there is pre-set |divider_position_|, use it. It can happen during
     // tablet <-> clamshell transition or multi-user transition.
@@ -1188,6 +1186,10 @@ void SplitViewController::OnAccessibilityStatusChanged() {
     EndSplitView();
 }
 
+void SplitViewController::OnAccessibilityControllerShutdown() {
+  Shell::Get()->accessibility_controller()->RemoveObserver(this);
+}
+
 void SplitViewController::StartObserving(aura::Window* window) {
   if (window && !window->HasObserver(this)) {
     Shell::Get()->shadow_controller()->UpdateShadowForWindow(window);

ash/wm/splitview/split_view_controller.h

@@ -212,6 +212,7 @@ class ASH_EXPORT SplitViewController : public SplitViewNotifier,
 
   // AccessibilityObserver:
   void OnAccessibilityStatusChanged() override;
+  void OnAccessibilityControllerShutdown() override;
 
   aura::Window* left_window() { return left_window_; }
   aura::Window* right_window() { return right_window_; }

ash/wm/workspace/backdrop_controller.cc

@@ -113,7 +113,7 @@ BackdropController::BackdropController(aura::Window* container)
     : container_(container) {
   DCHECK(container_);
   auto* shell = Shell::Get();
-  shell->AddShellObserver(this);
+  shell->split_view_controller()->AddObserver(this);
   shell->overview_controller()->AddObserver(this);
   shell->accessibility_controller()->AddObserver(this);
   shell->wallpaper_controller()->AddObserver(this);
@@ -129,7 +129,7 @@ BackdropController::~BackdropController() {
   shell->wallpaper_controller()->RemoveObserver(this);
   if (shell->overview_controller())
     shell->overview_controller()->RemoveObserver(this);
-  shell->RemoveShellObserver(this);
+  shell->split_view_controller()->RemoveObserver(this);
   // TODO(oshima): animations won't work right with mus:
   // http://crbug.com/548396.
   Hide(/*destroy=*/true);
@@ -210,14 +210,6 @@ aura::Window* BackdropController::GetTopmostWindowWithBackdrop() {
   return nullptr;
 }
 
-void BackdropController::OnSplitViewModeStarting() {
-  Shell::Get()->split_view_controller()->AddObserver(this);
-}
-
-void BackdropController::OnSplitViewModeEnded() {
-  Shell::Get()->split_view_controller()->RemoveObserver(this);
-}
-
 void BackdropController::OnOverviewModeStarting() {
   // Don't destroy backdrops, just hide them so they don't show in the overview
   // grid, but keep the widget so that it can be mirrored into the mini_desk

ash/wm/workspace/backdrop_controller.h

@@ -12,7 +12,6 @@
 #include "ash/public/cpp/split_view.h"
 #include "ash/public/cpp/tablet_mode_observer.h"
 #include "ash/public/cpp/wallpaper_controller_observer.h"
-#include "ash/shell_observer.h"
 #include "ash/wm/overview/overview_observer.h"
 #include "base/macros.h"
 #include "ui/gfx/geometry/rect.h"
@@ -41,7 +40,6 @@ namespace ash {
 //        - Bottom-most snapped window in splitview,
 //        - Top-most activatable window if splitview is inactive.
 class ASH_EXPORT BackdropController : public AccessibilityObserver,
-                                      public ShellObserver,
                                       public OverviewObserver,
                                       public SplitViewObserver,
                                       public WallpaperControllerObserver,
@@ -70,10 +68,6 @@ class ASH_EXPORT BackdropController : public AccessibilityObserver,
 
   aura::Window* backdrop_window() { return backdrop_window_; }
 
-  // ShellObserver:
-  void OnSplitViewModeStarting() override;
-  void OnSplitViewModeEnded() override;
-
   // OverviewObserver:
   void OnOverviewModeStarting() override;
   void OnOverviewModeEnding(OverviewSession* overview_session) override;