Prevent crash on clear-all button in message center

ui/message_center/views/message_list_view.cc

 // Copyright (c) 2015 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 <algorithm>
 
 #include "base/command_line.h"
 #include "base/location.h"
 #include "base/message_loop/message_loop.h"
 #include "base/single_thread_task_runner.h"
@@ skipping 284 matching lines @@
     views::BoundsAnimator* animator) {
   DCHECK_EQ(&animator_, animator);
   for (auto* view : deleted_when_done_) {
     const gfx::SlideAnimation* animation = animator->GetAnimationForView(view);
     if (animation)
       view->layer()->SetOpacity(animation->CurrentValueBetween(1.0, 0.0));
   }
 }
 
 void MessageListView::OnBoundsAnimatorDone(views::BoundsAnimator* animator) {
+  bool need_update = false;
+
+  if (clear_all_started_) {
+    clear_all_started_ = false;
+    // TODO(yoshiki): we shouldn't touch views in OnAllNotificationsCleared().
+    // Or rename it to like OnAllNotificationsClearing().
+    for (auto& observer : observers_)
+      observer.OnAllNotificationsCleared();
+
+    if (!deleted_when_done_.empty())

[Eliot Courtney, 2017/06/01 07:53:16]

Could you add a comment about why we need to call DoUpdateIfPossible() in this
case?

[yoshiki, 2017/06/01 08:31:48]

Done.

+      need_update = true;
+  }
+
+  // Ensures that the views are not destroyed yet.

[Eliot Courtney, 2017/06/01 07:53:16]

Since this is a DCHECK, maybe "None of these views should be deleted already.",
since it doesn't ensure anything.

[yoshiki, 2017/06/01 08:31:48]

Done.

+  DCHECK(std::all_of(deleted_when_done_.begin(), deleted_when_done_.end(),
+                     [this](views::View* view) { return Contains(view); }));
+
   for (auto* view : deleted_when_done_)
     delete view;
   deleted_when_done_.clear();
 
-  if (clear_all_started_) {
-    clear_all_started_ = false;
-    for (auto& observer : observers_)
-      observer.OnAllNotificationsCleared();
+  if (has_deferred_task_) {
+    has_deferred_task_ = false;
+    need_update = true;
   }
 
-  if (has_deferred_task_) {
-    has_deferred_task_ = false;
+  if (need_update)
     DoUpdateIfPossible();
-  }
 
   if (GetWidget())
     GetWidget()->SynthesizeMouseMoveEvent();
 
   if (quit_message_loop_after_animation_for_test_)
     base::MessageLoop::current()->QuitWhenIdle();
 }
 
 bool MessageListView::IsValidChild(const views::View* child) const {
   return child->visible() &&
@@ skipping 243 matching lines @@
         base::TimeDelta::FromMilliseconds(
             kAnimateClearingNextNotificationDelayMS));
   }
 }
 
 void MessageListView::SetRepositionTargetForTest(const gfx::Rect& target_rect) {
   SetRepositionTarget(target_rect);
 }
 
 }  // namespace message_center