[ash-md] Corrects a crash when a window is closed after leaving overview

Exiting overview mode may leave overview header widget still animating.
It is important not to attempt any window manipulation such as
re-stacking when the animation completes because the affected windows
may be gone by then.

BUG=646350
TEST=WindowSelectorTest.SafeToDestroyWindowDuringAnimation

Review-Url: https://codereview.chromium.org/2337383003
Cr-Commit-Position: refs/heads/master@{#418780}

ash/common/wm/overview/window_selector_item.cc

@@ -33,6 +33,7 @@
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/compositor/layer_animation_sequence.h"
 #include "ui/compositor/scoped_animation_duration_scale_mode.h"
+#include "ui/gfx/animation/slide_animation.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/color_utils.h"
 #include "ui/gfx/geometry/safe_integer_conversions.h"
@@ -197,7 +198,10 @@ class WindowSelectorItem::RoundedContainerView
 
   ~RoundedContainerView() override { StopObservingLayerAnimations(); }
 
-  void OnItemRestored() { item_ = nullptr; }
+  void OnItemRestored() {
+    item_ = nullptr;
+    item_window_ = nullptr;
+  }
 
   // Starts observing layer animations so that actions can be taken when
   // particular animations (opacity) complete. It should only be called once
@@ -216,6 +220,9 @@ class WindowSelectorItem::RoundedContainerView
     layer_ = nullptr;
   }
 
+  // Used by tests to set animation state.
+  gfx::SlideAnimation* animation() { return animation_.get(); }
+
   void set_color(SkColor target_color) { target_color_ = target_color; }
 
   // Starts a color animation using |tween_type|. The animation will change the
@@ -896,4 +903,8 @@ void WindowSelectorItem::FadeOut(std::unique_ptr<views::Widget> widget) {
   widget_ptr->SetOpacity(0.f);
 }
 
+gfx::SlideAnimation* WindowSelectorItem::GetBackgroundViewAnimation() {
+  return background_view_ ? background_view_->animation() : nullptr;
+}
+
 }  // namespace ash

ash/common/wm/overview/window_selector_item.h

@@ -18,6 +18,10 @@
 #include "ui/views/controls/button/label_button.h"
 #include "ui/views/widget/widget.h"
 
+namespace gfx {
+class SlideAnimation;
+}
+
 namespace views {
 class ImageButton;
 }
@@ -201,6 +205,9 @@ class ASH_EXPORT WindowSelectorItem : public views::ButtonListener,
   // Fades out a window caption when exiting overview mode.
   void FadeOut(std::unique_ptr<views::Widget> widget);
 
+  // Allows a test to directly set animation state.
+  gfx::SlideAnimation* GetBackgroundViewAnimation();
+
   static bool hide_header() { return use_mask_ || use_shape_; }
 
   // True if the item is being shown in the overview, false if it's being

ash/wm/overview/window_selector_unittest.cc

@@ -60,6 +60,7 @@
 #include "ui/display/manager/display_layout.h"
 #include "ui/events/event_utils.h"
 #include "ui/events/test/event_generator.h"
+#include "ui/gfx/animation/slide_animation.h"
 #include "ui/gfx/geometry/point_conversions.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/geometry/safe_integer_conversions.h"
@@ -273,6 +274,13 @@ class WindowSelectorTest
     return *iter;
   }
 
+  gfx::SlideAnimation* GetBackgroundViewAnimationForWindow(
+      int grid_index,
+      aura::Window* window) {
+    return GetWindowItemForWindow(grid_index, window)
+        ->GetBackgroundViewAnimation();
+  }
+
   // Selects |window| in the active overview session by cycling through all
   // windows in overview until it is found. Returns true if |window| was found,
   // false otherwise.
@@ -1286,6 +1294,38 @@ TEST_P(WindowSelectorTest, DISABLED_MinimizedWindowVisibility) {
   }
 }
 
+// Tests that it is safe to destroy a window while the overview header animation
+// is still active. See http://crbug.com/646350.
+TEST_P(WindowSelectorTest, SafeToDestroyWindowDuringAnimation) {
+  gfx::Rect bounds(0, 0, 400, 400);
+  {
+    // Quickly enter and exit overview mode to activate header animations.
+    std::unique_ptr<aura::Window> window(CreateWindow(bounds));
+    ui::ScopedAnimationDurationScaleMode test_duration_mode(
+        ui::ScopedAnimationDurationScaleMode::NON_ZERO_DURATION);
+    ToggleOverview();
+    EXPECT_TRUE(IsSelecting());
+
+    gfx::SlideAnimation* animation =
+        GetBackgroundViewAnimationForWindow(0, window.get());
+    if (ash::MaterialDesignController::IsOverviewMaterial())
+      ASSERT_NE(nullptr, animation);
+    ToggleOverview();
+    EXPECT_FALSE(IsSelecting());
+    if (animation)
+      EXPECT_TRUE(animation->is_animating());
+
+    // Close the window while the overview header animation is active.
+    window.reset();
+
+    // Progress animation to the end - should not crash.
+    if (animation) {
+      animation->SetCurrentValue(1.0);
+      animation->Reset(1.0);
+    }
+  }
+}
+
 // Tests that a bounds change during overview is corrected for.
 TEST_P(WindowSelectorTest, BoundsChangeDuringOverview) {
   std::unique_ptr<aura::Window> window(CreateWindow(gfx::Rect(0, 0, 400, 400)));