[ash-md] Animates overview shield in and out

ash/common/wm/overview/window_selector_controller.cc

 // Copyright 2013 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/overview/window_selector_controller.h"
 
 #include <vector>
 
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/system/tray/system_tray_delegate.h"
 #include "ash/common/wm/mru_window_tracker.h"
 #include "ash/common/wm/overview/window_selector.h"
 #include "ash/common/wm/window_state.h"
 #include "ash/common/wm_shell.h"
 #include "ash/common/wm_window.h"
 #include "base/metrics/histogram.h"
 
 namespace ash {
 
 WindowSelectorController::WindowSelectorController() {}
 
-WindowSelectorController::~WindowSelectorController() {}
+WindowSelectorController::~WindowSelectorController() {
+  // Destroy widgets that may be still animating if shell shuts down soon after
+  // exiting overview mode.
+  for (std::unique_ptr<DelayedAnimationObserver>& animation_observer :
+       delayed_animations_) {
+    animation_observer->Shutdown();
+  }
+}
 
 // static
 bool WindowSelectorController::CanSelect() {
   // Don't allow a window overview if the screen is locked or a modal dialog is
   // open or running in kiosk app session.
   SessionStateDelegate* session_state_delegate =
       WmShell::Get()->GetSessionStateDelegate();
   return session_state_delegate->IsActiveUserSessionStarted() &&
          !session_state_delegate->IsScreenLocked() &&
          !WmShell::Get()->IsSystemModalWindowOpen() &&
@@ skipping 39 matching lines @@
 
 // TODO(flackr): Make WindowSelectorController observe the activation of
 // windows, so we can remove WindowSelectorDelegate.
 void WindowSelectorController::OnSelectionEnded() {
   window_selector_->Shutdown();
   window_selector_.reset();
   last_selection_time_ = base::Time::Now();
   WmShell::Get()->OnOverviewModeEnded();
 }
 
+void WindowSelectorController::AddDelayedAnimationObserver(
+    std::unique_ptr<DelayedAnimationObserver> animation_observer) {
+  animation_observer->SetDelegate(this);
+  delayed_animations_.push_back(std::move(animation_observer));
+}
+
+void WindowSelectorController::RemoveDelayedAnimationObserver(

[bruthig, 2016/07/15 17:05:38]

This is only implemented correctly if called from within the
CleanupWidgetAfterAnimationObserver::OnImplicitAnimationsCompleted() function. 
If |animation_observer| is still active and this is called before
OnImplicitAnimationsCompleted() is, then I believe some bad things may happen.

e.g.
1. the |animation_observer| is destroyed
2. |animation_observer->widget_| is destroyed
3. |animation_observer|->OnImplicitAnimationsCompleted() will be called
4. the |animation_observer| will NOT be removed from the WindowSelectorDelegate
because |widget_| is null.
5. When the WindowSelectorDelegate is destroyed it will try to double delete the
|animation_observer|

Perhaps we should support this use case, detect it somehow with a DCHECK(), or
add a comment.

[varkha, 2016/07/15 18:53:36]

Done (Added some comment in the RemoveDelayedAnimationObserver doc).

+    DelayedAnimationObserver* animation_observer) {
+  class IsEqual {
+   public:
+    explicit IsEqual(DelayedAnimationObserver* animation_observer)
+        : animation_observer_(animation_observer) {}
+    bool operator()(const std::unique_ptr<DelayedAnimationObserver>& other) {
+      return (other.get() == animation_observer_);
+    }
+
+   private:
+    const DelayedAnimationObserver* animation_observer_;
+  };
+  delayed_animations_.erase(
+      std::remove_if(delayed_animations_.begin(), delayed_animations_.end(),
+                     IsEqual(animation_observer)),
+      delayed_animations_.end());
+}
+
 void WindowSelectorController::OnSelectionStarted() {
   if (!last_selection_time_.is_null()) {
     UMA_HISTOGRAM_LONG_TIMES("Ash.WindowSelector.TimeBetweenUse",
                              base::Time::Now() - last_selection_time_);
   }
 }
 
 }  // namespace ash