[Notifications] Fix crashes.

ui/arc/notification/arc_custom_notification_view.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 "ui/arc/notification/arc_custom_notification_view.h"
 
 #include "ash/wm/window_util.h"
 #include "base/auto_reset.h"
 #include "base/memory/ptr_util.h"
 #include "components/exo/notification_surface.h"
@@ skipping 276 matching lines @@
   settings_button_ = new ControlButton(this);
   settings_button_->SetImage(views::CustomButton::STATE_NORMAL,
                              message_center::GetSettingsIcon());
   settings_button_->SetAccessibleName(l10n_util::GetStringUTF16(
       IDS_MESSAGE_NOTIFICATION_SETTINGS_BUTTON_ACCESSIBLE_NAME));
   settings_button_->SetTooltipText(l10n_util::GetStringUTF16(
       IDS_MESSAGE_NOTIFICATION_SETTINGS_BUTTON_ACCESSIBLE_NAME));
   control_buttons_view_->AddChildView(settings_button_);
 }
 
-void ArcCustomNotificationView::CreateFloatingControlButtons() {
+void ArcCustomNotificationView::MaybeCreateFloatingControlButtons() {
   // Floating close button is a transient child of |surface_| and also part
   // of the hosting widget's focus chain. It could only be created when both
-  // are present.
-  if (!surface_ || !GetWidget())
+  // are present. Further, if we are being destroyed (|item_| is null), don't
+  // create the control buttons.
+  if (!surface_ || !GetWidget() || !item_)
     return;
 
   // Creates the control_buttons_view_, which collects all control buttons into
   // a horizontal box.
   control_buttons_view_ = new views::View();
   control_buttons_view_->SetLayoutManager(
       new views::BoxLayout(views::BoxLayout::kHorizontal, 0, 0, 0));
 
-  if (item_ && item_->IsOpeningSettingsSupported())
+  if (item_->IsOpeningSettingsSupported())
     CreateSettingsButton();
-  if (item_ && !item_->pinned())
+  if (!item_->pinned())
     CreateCloseButton();
 
   views::Widget::InitParams params(views::Widget::InitParams::TYPE_CONTROL);
   params.opacity = views::Widget::InitParams::TRANSLUCENT_WINDOW;
   params.ownership = views::Widget::InitParams::WIDGET_OWNS_NATIVE_WIDGET;
   params.parent = surface_->window();
 
   floating_control_buttons_widget_.reset(new views::Widget);
   floating_control_buttons_widget_->Init(params);
   floating_control_buttons_widget_->SetContentsView(control_buttons_view_);
@@ skipping 20 matching lines @@
     surface_->window()->RemoveObserver(this);
     surface_->window()->RemovePreTargetHandler(event_forwarder_.get());
   }
 
   surface_ = surface;
 
   if (surface_ && surface_->window()) {
     surface_->window()->AddObserver(this);
     surface_->window()->AddPreTargetHandler(event_forwarder_.get());
 
-    CreateFloatingControlButtons();
+    MaybeCreateFloatingControlButtons();
 
     if (GetWidget())
       AttachSurface();
   }
 }
 
+// N.B. |UpdatePreferredSize| calls SetPreferredSize, which may update the
+// notification. If this is during a clear all operation, we may receive an
+// OnItemDestroying event. That is, calling this method may indirectly cause

[yhanada1, 2017/04/21 08:06:49]

method?

[Eliot Courtney, 2017/04/25 04:09:24]

With crrev.com/2833403002 this comment is no longer accurate, so I removed it.

+// item_ to become null.
 void ArcCustomNotificationView::UpdatePreferredSize() {
   gfx::Size preferred_size =
       surface_ ? surface_->GetSize() : item_ ? item_->snapshot().size()
                                              : gfx::Size();
   if (preferred_size.IsEmpty())
     return;
 
   if (preferred_size.width() != message_center::kNotificationWidth) {
     const float scale = static_cast<float>(message_center::kNotificationWidth) /
                         preferred_size.width();
     preferred_size.SetSize(message_center::kNotificationWidth,
                            preferred_size.height() * scale);
   }
 
   SetPreferredSize(preferred_size);
 }
 
 void ArcCustomNotificationView::UpdateControlButtonsVisibility() {
   if (!surface_)
     return;
 
-  if (!floating_control_buttons_widget_) {
-    if (GetWidget())
-      CreateFloatingControlButtons();
-    else
-      return;
-  }
+  if (!floating_control_buttons_widget_)
+    MaybeCreateFloatingControlButtons();
+  if (!floating_control_buttons_widget_)

[yoshiki, 2017/04/21 15:21:38]

I think the following structure is better for readability.
if (!floating_control_buttons_widget_) {
  MaybeCreateFloatingControlButtons();
  if (!floating_control_buttons_widget_)
    return;
}

Please mention that floating_control_buttons_widget_ may be updated in
MaybeCreateFloatingControlButtons().

[Eliot Courtney, 2017/04/25 04:09:24]

Done.

+    return;
 
   const bool target_visiblity =
       IsMouseHovered() || (close_button_ && close_button_->HasFocus()) ||
       (settings_button_ && settings_button_->HasFocus());
   if (target_visiblity == floating_control_buttons_widget_->IsVisible())
     return;
 
   if (target_visiblity)
     floating_control_buttons_widget_->Show();
   else
     floating_control_buttons_widget_->Hide();
 }
 
 void ArcCustomNotificationView::UpdatePinnedState() {
-  DCHECK(item_);
+  if (!item_)
+    return;
 
   if (item_->pinned() && close_button_) {
     control_buttons_view_->RemoveChildView(close_button_.get());
     close_button_.reset();
     Layout();
   } else if (!item_->pinned() && !close_button_) {
     CreateCloseButton();
     Layout();
   }
 }
@@ skipping 33 matching lines @@
 
 void ArcCustomNotificationView::StartControlButtonsColorAnimation() {
   if (control_button_color_animation_)
     control_button_color_animation_->End();
   control_button_color_animation_.reset(new gfx::LinearAnimation(this));
   control_button_color_animation_->SetDuration(kBackgroundColorChangeDuration);
   control_button_color_animation_->Start();
 }
 
 bool ArcCustomNotificationView::ShouldUpdateControlButtonsColor() const {
-  DCHECK(item_);
+  // Don't update the control button color when we are about to be destroyed.
+  if (!item_)
+   return false;

[yoshiki, 2017/04/21 15:21:38]

I think it's better to check item_ in the caller instead of here for
consistency. But it's up to you.

[Eliot Courtney, 2017/04/25 04:09:24]

I thought it would be good to create preconditions at the top of every function.
This function accesses item_ so I figured it'd be better to check it close to
the access.

 
   if (settings_button_ &&
       settings_button_->background()->get_color() !=
           GetControlButtonBackgroundColor(item_->shown_contents()))
     return true;
   if (close_button_ &&
       close_button_->background()->get_color() !=
           GetControlButtonBackgroundColor(item_->shown_contents()))
     return true;
   return false;
@@ skipping 252 matching lines @@
     }
     if (close_button_) {
       close_button_->set_background(
           views::Background::CreateSolidBackground(current_color));
       close_button_->SchedulePaint();
     }
   }
 }
 
 }  // namespace arc