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

ash/wm/overview/window_selector_unittest.cc

Index: ash/wm/overview/window_selector_unittest.cc
diff --git a/ash/wm/overview/window_selector_unittest.cc b/ash/wm/overview/window_selector_unittest.cc
index 9042d0eaddbee8c86c176ccbb45c84e2a53f063e..e58d821634b54f45580dabaf216846ee76de5990 100644
--- a/ash/wm/overview/window_selector_unittest.cc
+++ b/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_TRUE(!!animation);

[sky, 2016/09/15 03:01:00]

Double negatives are hard to read. ASSERT_NE(nullptr, animation) states
intention much better.

[varkha, 2016/09/15 03:54:18]

Done.

+    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)));