Move AccessibilityDelegate ownership to ash::WmShell

ash/common/wm_shell.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/common/wm_shell.h"
 
 #include <utility>
 
+#include "ash/common/accessibility_delegate.h"
 #include "ash/common/focus_cycler.h"
 #include "ash/common/keyboard/keyboard_ui.h"
 #include "ash/common/shell_delegate.h"
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/system/brightness_control_delegate.h"
 #include "ash/common/system/keyboard_brightness_control_delegate.h"
 #include "ash/common/system/tray/system_tray_delegate.h"
 #include "ash/common/system/tray/system_tray_notifier.h"
 #include "ash/common/wm/maximize_mode/maximize_mode_controller.h"
 #include "ash/common/wm/mru_window_tracker.h"
@@ skipping 19 matching lines @@
 }
 
 // static
 WmShell* WmShell::Get() {
   return instance_;
 }
 
 void WmShell::Initialize() {
   // Some delegates access WmShell during their construction. Create them here
   // instead of the WmShell constructor.
+  accessibility_delegate_.reset(delegate_->CreateAccessibilityDelegate());
   media_delegate_.reset(delegate_->CreateMediaDelegate());
 }
 
+void WmShell::Shutdown() {
+  media_delegate_.reset();

[James Cook, 2016/07/14 23:31:46]

Not strictly necessary, but a little clearer I think.

[msw, 2016/07/15 15:33:14]

I'd be wary of adding explicit destruction if none is needed. Shell has plenty
of relative lifetime (ctor/dtor ordering) issues, and this may imply that these
members need to be destroyed before the dtor or in some specific order. WDYT?

Maybe copy the comment from shell.cc if it applies to |accessibility_delegate_|:
  // Depends on |focus_client_|, so must be destroyed before.

[James Cook, 2016/07/15 17:03:06]

Done. Removed media_delegate_.reset(). Added a comment that
accessibility_delegate_ accesses WmShell in its destructor, which is the actual
problem.

+  accessibility_delegate_.reset();
+}
+
 void WmShell::OnMaximizeModeStarted() {
   FOR_EACH_OBSERVER(ShellObserver, shell_observers_, OnMaximizeModeStarted());
 }
 
 void WmShell::OnMaximizeModeEnded() {
   FOR_EACH_OBSERVER(ShellObserver, shell_observers_, OnMaximizeModeEnded());
 }
 
 void WmShell::NotifyPinnedStateChanged(WmWindow* pinned_window) {
   FOR_EACH_OBSERVER(ShellObserver, shell_observers_,
@@ skipping 86 matching lines @@
 
 void WmShell::CreateMruWindowTracker() {
   mru_window_tracker_.reset(new MruWindowTracker);
 }
 
 void WmShell::DeleteMruWindowTracker() {
   mru_window_tracker_.reset();
 }
 
 }  // namespace ash