Fixing race conditions in ui::content::WindowSlider which could cause the overscroll overlay to nev…

content/browser/web_contents/aura/window_slider_unittest.cc

 // Copyright (c) 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 "content/browser/web_contents/aura/window_slider.h"
 
 #include "base/bind.h"
+#include "base/time/time.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/aura/test/aura_test_base.h"
 #include "ui/aura/test/event_generator.h"
 #include "ui/aura/test/test_window_delegate.h"
 #include "ui/aura/window.h"
 #include "ui/base/hit_test.h"
+#include "ui/compositor/scoped_animation_duration_scale_mode.h"
+#include "ui/compositor/scoped_layer_animation_settings.h"
+#include "ui/compositor/test/layer_animator_test_controller.h"
 #include "ui/events/event_processor.h"
+#include "ui/events/event_utils.h"
+#include "ui/gfx/frame_time.h"
 
 namespace content {
 
 void DispatchEventDuringScrollCallback(ui::EventProcessor* dispatcher,
                                        ui::Event* event,
                                        ui::EventType type,
                                        const gfx::Vector2dF& delta) {
   if (type != ui::ET_GESTURE_SCROLL_UPDATE)
     return;
   ui::EventDispatchDetails details = dispatcher->OnEventFromSource(event);
   CHECK(!details.dispatcher_destroyed);
 }
 
 void ChangeSliderOwnerDuringScrollCallback(scoped_ptr<aura::Window>* window,
                                            WindowSlider* slider,
                                            ui::EventType type,
                                            const gfx::Vector2dF& delta) {
   if (type != ui::ET_GESTURE_SCROLL_UPDATE)
     return;
   aura::Window* new_window = new aura::Window(NULL);
   new_window->Init(aura::WINDOW_LAYER_TEXTURED);
   new_window->Show();
   slider->ChangeOwner(new_window);
   (*window)->parent()->AddChild(new_window);
   window->reset(new_window);
 }
 
+void ConfirmSlideDuringScrollCallback(WindowSlider* slider,
+                                      ui::EventType type,
+                                      const gfx::Vector2dF& delta) {
+  static float total_delta_x = 0;
+  if (type == ui::ET_GESTURE_SCROLL_BEGIN)
+    total_delta_x = 0;
+
+  if (type == ui::ET_GESTURE_SCROLL_UPDATE) {
+    total_delta_x += delta.x();
+    if (total_delta_x >= 70)
+      EXPECT_TRUE(slider->IsSlideInProgress());
+  } else {
+    EXPECT_FALSE(slider->IsSlideInProgress());
+  }
+}
+
+void ConfirmNoSlideDuringScrollCallback(WindowSlider* slider,
+                                        ui::EventType type,
+                                        const gfx::Vector2dF& delta) {
+  EXPECT_FALSE(slider->IsSlideInProgress());
+}
+
 // The window delegate does not receive any events.
 class NoEventWindowDelegate : public aura::test::TestWindowDelegate {
  public:
   NoEventWindowDelegate() {
   }
   virtual ~NoEventWindowDelegate() {}
 
  private:
   // Overridden from aura::WindowDelegate:
   virtual bool HasHitTestMask() const OVERRIDE { return true; }
 
   DISALLOW_COPY_AND_ASSIGN(NoEventWindowDelegate);
 };
 
 class WindowSliderDelegateTest : public WindowSlider::Delegate {
  public:
   WindowSliderDelegateTest()
       : can_create_layer_(true),
         created_back_layer_(false),
         created_front_layer_(false),
+        slide_completing_(false),
         slide_completed_(false),
         slide_aborted_(false),
         slider_destroyed_(false) {
   }
-  virtual ~WindowSliderDelegateTest() {}
+  virtual ~WindowSliderDelegateTest() {
+    // Make sure slide_completed() gets called if slide_completing() was called.
+    CHECK(!slide_completing_ || slide_completed_);
+  }
 
   void Reset() {
     can_create_layer_ = true;
     created_back_layer_ = false;
     created_front_layer_ = false;
+    slide_completing_ = false;
     slide_completed_ = false;
     slide_aborted_ = false;
     slider_destroyed_ = false;
   }
 
   void SetCanCreateLayer(bool can_create_layer) {
     can_create_layer_ = can_create_layer;
   }
 
   bool created_back_layer() const { return created_back_layer_; }
   bool created_front_layer() const { return created_front_layer_; }
+  bool slide_completing() const { return slide_completing_; }
   bool slide_completed() const { return slide_completed_; }
   bool slide_aborted() const { return slide_aborted_; }
   bool slider_destroyed() const { return slider_destroyed_; }
 
  protected:
   ui::Layer* CreateLayerForTest() {
     CHECK(can_create_layer_);
     ui::Layer* layer = new ui::Layer(ui::LAYER_SOLID_COLOR);
     layer->SetColor(SK_ColorRED);
     return layer;
   }
 
   // Overridden from WindowSlider::Delegate:
   virtual ui::Layer* CreateBackLayer() OVERRIDE {
     if (!can_create_layer_)
       return NULL;
     created_back_layer_ = true;
     return CreateLayerForTest();
   }
 
   virtual ui::Layer* CreateFrontLayer() OVERRIDE {
     if (!can_create_layer_)
       return NULL;
     created_front_layer_ = true;
     return CreateLayerForTest();
   }
 
-  virtual void OnWindowSlideComplete() OVERRIDE {
+  virtual void OnWindowSlideCompleted() OVERRIDE {
     slide_completed_ = true;
   }
 
+  virtual void OnWindowSlideCompleting() OVERRIDE {
+    slide_completing_ = true;
+  }
+
   virtual void OnWindowSlideAborted() OVERRIDE {
     slide_aborted_ = true;
   }
 
   virtual void OnWindowSliderDestroyed() OVERRIDE {
     slider_destroyed_ = true;
   }
 
  private:
   bool can_create_layer_;
   bool created_back_layer_;
   bool created_front_layer_;
+  bool slide_completing_;
   bool slide_completed_;
   bool slide_aborted_;
   bool slider_destroyed_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowSliderDelegateTest);
 };
 
 // This delegate destroys the owner window when the slider is destroyed.
 class WindowSliderDeleteOwnerOnDestroy : public WindowSliderDelegateTest {
  public:
@@ skipping 16 matching lines @@
 // This delegate destroyes the owner window when a slide is completed.
 class WindowSliderDeleteOwnerOnComplete : public WindowSliderDelegateTest {
  public:
   explicit WindowSliderDeleteOwnerOnComplete(aura::Window* owner)
       : owner_(owner) {
   }
   virtual ~WindowSliderDeleteOwnerOnComplete() {}
 
  private:
   // Overridden from WindowSlider::Delegate:
-  virtual void OnWindowSlideComplete() OVERRIDE {
-    WindowSliderDelegateTest::OnWindowSlideComplete();
+  virtual void OnWindowSlideCompleted() OVERRIDE {
+    WindowSliderDelegateTest::OnWindowSlideCompleted();
     delete owner_;
   }
 
   aura::Window* owner_;
   DISALLOW_COPY_AND_ASSIGN(WindowSliderDeleteOwnerOnComplete);
 };
 
 typedef aura::test::AuraTestBase WindowSliderTest;
 
 TEST_F(WindowSliderTest, WindowSlideUsingGesture) {
   scoped_ptr<aura::Window> window(CreateNormalWindow(0, root_window(), NULL));
   window->SetBounds(gfx::Rect(0, 0, 400, 400));
   WindowSliderDelegateTest slider_delegate;
 
   aura::test::EventGenerator generator(root_window());
 
   // Generate a horizontal overscroll.
   WindowSlider* slider =
       new WindowSlider(&slider_delegate, root_window(), window.get());
-  generator.GestureScrollSequence(gfx::Point(10, 10),
-                                  gfx::Point(180, 10),
-                                  base::TimeDelta::FromMilliseconds(10),
-                                  10);
+  generator.GestureScrollSequenceWithCallback(
+      gfx::Point(10, 10),
+      gfx::Point(180, 10),
+      base::TimeDelta::FromMilliseconds(10),
+      10,
+      base::Bind(&ConfirmSlideDuringScrollCallback, slider));
   EXPECT_TRUE(slider_delegate.created_back_layer());
+  EXPECT_TRUE(slider_delegate.slide_completing());
   EXPECT_TRUE(slider_delegate.slide_completed());
   EXPECT_FALSE(slider_delegate.created_front_layer());
   EXPECT_FALSE(slider_delegate.slide_aborted());
   EXPECT_FALSE(slider_delegate.slider_destroyed());
   EXPECT_FALSE(slider->IsSlideInProgress());
   slider_delegate.Reset();
   window->SetTransform(gfx::Transform());
 
-  // Generat a horizontal overscroll in the reverse direction.
-  generator.GestureScrollSequence(gfx::Point(180, 10),
-                                  gfx::Point(10, 10),
-                                  base::TimeDelta::FromMilliseconds(10),
-                                  10);
+  // Generate a horizontal overscroll in the reverse direction.
+  generator.GestureScrollSequenceWithCallback(
+      gfx::Point(180, 10),
+      gfx::Point(10, 10),
+      base::TimeDelta::FromMilliseconds(10),
+      10,
+      base::Bind(&ConfirmSlideDuringScrollCallback, slider));
   EXPECT_TRUE(slider_delegate.created_front_layer());
+  EXPECT_TRUE(slider_delegate.slide_completing());
   EXPECT_TRUE(slider_delegate.slide_completed());
   EXPECT_FALSE(slider_delegate.created_back_layer());
   EXPECT_FALSE(slider_delegate.slide_aborted());
   EXPECT_FALSE(slider_delegate.slider_destroyed());
   EXPECT_FALSE(slider->IsSlideInProgress());
   slider_delegate.Reset();
 
   // Generate a vertical overscroll.
-  generator.GestureScrollSequence(gfx::Point(10, 10),
-                                  gfx::Point(10, 80),
-                                  base::TimeDelta::FromMilliseconds(10),
-                                  10);
+  generator.GestureScrollSequenceWithCallback(
+      gfx::Point(10, 10),
+      gfx::Point(10, 80),
+      base::TimeDelta::FromMilliseconds(10),
+      10,
+      base::Bind(&ConfirmNoSlideDuringScrollCallback, slider));
   EXPECT_FALSE(slider_delegate.created_back_layer());
+  EXPECT_FALSE(slider_delegate.slide_completing());
   EXPECT_FALSE(slider_delegate.slide_completed());
   EXPECT_FALSE(slider_delegate.created_front_layer());
   EXPECT_FALSE(slider_delegate.slide_aborted());
   EXPECT_FALSE(slider->IsSlideInProgress());
   slider_delegate.Reset();
 
   // Generate a horizontal scroll that starts overscroll, but doesn't scroll
   // enough to complete it.
-  generator.GestureScrollSequence(gfx::Point(10, 10),
-                                  gfx::Point(80, 10),
-                                  base::TimeDelta::FromMilliseconds(10),
-                                  10);
+  generator.GestureScrollSequenceWithCallback(
+      gfx::Point(10, 10),
+      gfx::Point(80, 10),
+      base::TimeDelta::FromMilliseconds(10),
+      10,
+      base::Bind(&ConfirmSlideDuringScrollCallback, slider));
   EXPECT_TRUE(slider_delegate.created_back_layer());
   EXPECT_TRUE(slider_delegate.slide_aborted());
   EXPECT_FALSE(slider_delegate.created_front_layer());
+  EXPECT_FALSE(slider_delegate.slide_completing());
   EXPECT_FALSE(slider_delegate.slide_completed());
   EXPECT_FALSE(slider_delegate.slider_destroyed());
   EXPECT_FALSE(slider->IsSlideInProgress());
   slider_delegate.Reset();
 
   // Destroy the window. This should destroy the slider.
   window.reset();
   EXPECT_TRUE(slider_delegate.slider_destroyed());
 }
 
-// Tests that the window slide is cancelled when a different type of event
+// Tests that the window slide is interrupted when a different type of event
 // happens.
 TEST_F(WindowSliderTest, WindowSlideIsCancelledOnEvent) {
   scoped_ptr<aura::Window> window(CreateNormalWindow(0, root_window(), NULL));
+  window->SetBounds(gfx::Rect(0, 0, 400, 400));
   WindowSliderDelegateTest slider_delegate;
 
   ui::Event* events[] = {
     new ui::MouseEvent(ui::ET_MOUSE_MOVED,
                        gfx::Point(55, 10),
                        gfx::Point(55, 10),
                        0, 0),
     new ui::KeyEvent(ui::ET_KEY_PRESSED,
                      ui::VKEY_A,
                      0,
                      true),
     NULL
   };
 
   new WindowSlider(&slider_delegate, root_window(), window.get());
   for (int i = 0; events[i]; ++i) {
     // Generate a horizontal overscroll.
     aura::test::EventGenerator generator(root_window());
     generator.GestureScrollSequenceWithCallback(
         gfx::Point(10, 10),
         gfx::Point(80, 10),
         base::TimeDelta::FromMilliseconds(10),
         1,
         base::Bind(&DispatchEventDuringScrollCallback,
                    root_window()->GetHost()->event_processor(),
                    base::Owned(events[i])));
     EXPECT_TRUE(slider_delegate.created_back_layer());
     EXPECT_TRUE(slider_delegate.slide_aborted());
     EXPECT_FALSE(slider_delegate.created_front_layer());
+    EXPECT_FALSE(slider_delegate.slide_completing());
     EXPECT_FALSE(slider_delegate.slide_completed());
     EXPECT_FALSE(slider_delegate.slider_destroyed());
     slider_delegate.Reset();
   }
   window.reset();
   EXPECT_TRUE(slider_delegate.slider_destroyed());
 }
 
+// Tests that the window slide can continue after it is interrupted by another
+// event if the user continues scrolling.
+TEST_F(WindowSliderTest, WindowSlideInterruptedThenContinues) {
+  scoped_ptr<aura::Window> window(CreateNormalWindow(0, root_window(), NULL));
+  window->SetBounds(gfx::Rect(0, 0, 400, 400));
+  WindowSliderDelegateTest slider_delegate;
+
+  ui::ScopedAnimationDurationScaleMode normal_duration_(
+      ui::ScopedAnimationDurationScaleMode::NORMAL_DURATION);
+  ui::LayerAnimator* animator = window->layer()->GetAnimator();
+  gfx::AnimationContainerElement* element = animator;
+  animator->set_disable_timer_for_test(true);
+  ui::LayerAnimatorTestController test_controller(animator);
+
+  WindowSlider* slider =
+      new WindowSlider(&slider_delegate, root_window(), window.get());
+
+  ui::MouseEvent interrupt_event(ui::ET_MOUSE_MOVED,
+                                 gfx::Point(55, 10),
+                                 gfx::Point(55, 10),
+                                 0, 0);
+
+  aura::test::EventGenerator generator(root_window());
+
+  // Start the scroll sequence. Scroll forward so that |window|'s layer is the
+  // one animating.
+  const int kTouchId = 5;
+  ui::TouchEvent press(ui::ET_TOUCH_PRESSED,
+                       gfx::Point(10, 10),
+                       kTouchId,
+                       ui::EventTimeForNow());
+  generator.Dispatch(&press);
+
+  // First scroll event of the sequence.
+  ui::TouchEvent move1(ui::ET_TOUCH_MOVED,
+                       gfx::Point(100, 10),
+                       kTouchId,
+                       ui::EventTimeForNow());
+  generator.Dispatch(&move1);
+  EXPECT_TRUE(slider->IsSlideInProgress());
+  EXPECT_FALSE(animator->is_animating());
+  // Dispatch the event after the first scroll and confirm it interrupts the
+  // scroll and starts  the "reset slide" animation.
+  generator.Dispatch(&interrupt_event);
+  EXPECT_TRUE(slider->IsSlideInProgress());
+  EXPECT_TRUE(animator->is_animating());
+  EXPECT_TRUE(slider_delegate.created_back_layer());
+  // slide_aborted() should be false because the 'reset slide' animation
+  // hasn't completed yet.
+  EXPECT_FALSE(slider_delegate.slide_aborted());
+  EXPECT_FALSE(slider_delegate.created_front_layer());
+  EXPECT_FALSE(slider_delegate.slide_completing());
+  EXPECT_FALSE(slider_delegate.slide_completed());
+  EXPECT_FALSE(slider_delegate.slider_destroyed());
+  slider_delegate.Reset();
+
+  // Second scroll event of the sequence.
+  ui::TouchEvent move2(ui::ET_TOUCH_MOVED,
+                       gfx::Point(200, 10),
+                       kTouchId,
+                       ui::EventTimeForNow());
+  generator.Dispatch(&move2);
+  // The second scroll should instantly cause the animation to complete.
+  EXPECT_FALSE(animator->is_animating());
+  EXPECT_FALSE(slider_delegate.created_back_layer());
+  // The ResetScroll() animation was completed, so now slide_aborted()
+  // should be true.
+  EXPECT_TRUE(slider_delegate.slide_aborted());
+
+  // Third scroll event of the sequence.
+  ui::TouchEvent move3(ui::ET_TOUCH_MOVED,
+                       gfx::Point(300, 10),
+                       kTouchId,
+                       ui::EventTimeForNow());
+  generator.Dispatch(&move3);
+  // The third scroll should re-start the sliding.
+  EXPECT_TRUE(slider->IsSlideInProgress());
+  EXPECT_TRUE(slider_delegate.created_back_layer());
+
+  // Generate the release event, finishing the scroll sequence.
+  ui::TouchEvent release(ui::ET_TOUCH_RELEASED,
+                         gfx::Point(300, 10),
+                         kTouchId,
+                         ui::EventTimeForNow());
+  generator.Dispatch(&release);
+  // When the scroll gesture ends, the slide animation should start.
+  EXPECT_TRUE(slider->IsSlideInProgress());
+  EXPECT_TRUE(animator->is_animating());
+  EXPECT_TRUE(slider_delegate.slide_completing());
+  EXPECT_FALSE(slider_delegate.created_front_layer());
+  EXPECT_FALSE(slider_delegate.slide_completed());
+  EXPECT_FALSE(slider_delegate.slider_destroyed());
+
+  // Progress the animator to complete the slide animation.
+  ui::ScopedLayerAnimationSettings settings(animator);
+  base::TimeDelta duration = settings.GetTransitionDuration();
+  test_controller.StartThreadedAnimationsIfNeeded();
+  element->Step(gfx::FrameTime::Now() + duration);
+
+  EXPECT_TRUE(slider_delegate.slide_completed());
+  EXPECT_FALSE(slider_delegate.slider_destroyed());
+
+  window.reset();
+  EXPECT_TRUE(slider_delegate.slider_destroyed());
+}
+
 // Tests that the slide works correctly when the owner of the window changes
 // during the duration of the slide.
 TEST_F(WindowSliderTest, OwnerWindowChangesDuringWindowSlide) {
   scoped_ptr<aura::Window> parent(CreateNormalWindow(0, root_window(), NULL));
 
   NoEventWindowDelegate window_delegate;
   window_delegate.set_window_component(HTNOWHERE);
   scoped_ptr<aura::Window> window(CreateNormalWindow(1, parent.get(),
                                                      &window_delegate));
 
@@ skipping 10 matching lines @@
       gfx::Point(80, 10),
       base::TimeDelta::FromMilliseconds(10),
       1,
       base::Bind(&ChangeSliderOwnerDuringScrollCallback,
                  base::Unretained(&window),
                  slider.get()));
   aura::Window* new_window = window.get();
   EXPECT_NE(old_window, new_window);
 
   EXPECT_TRUE(slider_delegate.created_back_layer());
+  EXPECT_TRUE(slider_delegate.slide_completing());
   EXPECT_TRUE(slider_delegate.slide_completed());
   EXPECT_FALSE(slider_delegate.created_front_layer());
   EXPECT_FALSE(slider_delegate.slide_aborted());
   EXPECT_FALSE(slider_delegate.slider_destroyed());
 }
 
+// If the delegate doesn't create the layer to show while sliding, WindowSlider
+// shouldn't start the slide or change delegate's state in any way in response
+// to user input.
 TEST_F(WindowSliderTest, NoSlideWhenLayerCantBeCreated) {
   scoped_ptr<aura::Window> window(CreateNormalWindow(0, root_window(), NULL));
   window->SetBounds(gfx::Rect(0, 0, 400, 400));
   WindowSliderDelegateTest slider_delegate;
   slider_delegate.SetCanCreateLayer(false);
+  WindowSlider* slider =
+      new WindowSlider(&slider_delegate, root_window(), window.get());
 
   aura::test::EventGenerator generator(root_window());
 
-  // Generate a horizontal overscroll.
-  scoped_ptr<WindowSlider> slider(
-      new WindowSlider(&slider_delegate, root_window(), window.get()));
-  generator.GestureScrollSequence(gfx::Point(10, 10),
-                                  gfx::Point(160, 10),
-                                  base::TimeDelta::FromMilliseconds(10),
-                                  10);
+  // No slide in progress should be reported during scroll since the layer
+  // wasn't created.
+  generator.GestureScrollSequenceWithCallback(
+      gfx::Point(10, 10),
+      gfx::Point(180, 10),
+      base::TimeDelta::FromMilliseconds(10),
+      1,
+      base::Bind(&ConfirmNoSlideDuringScrollCallback, slider));
+
   EXPECT_FALSE(slider_delegate.created_back_layer());
+  EXPECT_FALSE(slider_delegate.slide_completing());
   EXPECT_FALSE(slider_delegate.slide_completed());
   EXPECT_FALSE(slider_delegate.created_front_layer());
   EXPECT_FALSE(slider_delegate.slide_aborted());
   EXPECT_FALSE(slider_delegate.slider_destroyed());
   window->SetTransform(gfx::Transform());
 
   slider_delegate.SetCanCreateLayer(true);
-  generator.GestureScrollSequence(gfx::Point(10, 10),
-                                  gfx::Point(160, 10),
-                                  base::TimeDelta::FromMilliseconds(10),
-                                  10);
+  generator.GestureScrollSequenceWithCallback(
+      gfx::Point(10, 10),
+      gfx::Point(180, 10),
+      base::TimeDelta::FromMilliseconds(10),
+      10,
+      base::Bind(&ConfirmSlideDuringScrollCallback, slider));
   EXPECT_TRUE(slider_delegate.created_back_layer());
+  EXPECT_TRUE(slider_delegate.slide_completing());
   EXPECT_TRUE(slider_delegate.slide_completed());
   EXPECT_FALSE(slider_delegate.created_front_layer());
   EXPECT_FALSE(slider_delegate.slide_aborted());
   EXPECT_FALSE(slider_delegate.slider_destroyed());
+
+  window.reset();
+  EXPECT_TRUE(slider_delegate.slider_destroyed());
 }
 
 // Tests that the owner window can be destroyed from |OnWindowSliderDestroyed()|
 // delegate callback without causing a crash.
 TEST_F(WindowSliderTest, OwnerIsDestroyedOnSliderDestroy) {
   size_t child_windows = root_window()->children().size();
   aura::Window* window = CreateNormalWindow(0, root_window(), NULL);
   window->SetBounds(gfx::Rect(0, 0, 400, 400));
   EXPECT_EQ(child_windows + 1, root_window()->children().size());
 
   WindowSliderDeleteOwnerOnDestroy slider_delegate(window);
   aura::test::EventGenerator generator(root_window());
 
   // Generate a horizontal overscroll.
   scoped_ptr<WindowSlider> slider(
       new WindowSlider(&slider_delegate, root_window(), window));
   generator.GestureScrollSequence(gfx::Point(10, 10),
                                   gfx::Point(180, 10),
                                   base::TimeDelta::FromMilliseconds(10),
                                   10);
   EXPECT_TRUE(slider_delegate.created_back_layer());
+  EXPECT_TRUE(slider_delegate.slide_completing());
   EXPECT_TRUE(slider_delegate.slide_completed());
   EXPECT_FALSE(slider_delegate.created_front_layer());
   EXPECT_FALSE(slider_delegate.slide_aborted());
   EXPECT_FALSE(slider_delegate.slider_destroyed());
 
   slider.reset();
   // Destroying the slider would have destroyed |window| too. So |window| should
   // not need to be destroyed here.
   EXPECT_EQ(child_windows, root_window()->children().size());
 }
 
 // Tests that the owner window can be destroyed from |OnWindowSlideComplete()|
 // delegate callback without causing a crash.
 TEST_F(WindowSliderTest, OwnerIsDestroyedOnSlideComplete) {
   size_t child_windows = root_window()->children().size();
   aura::Window* window = CreateNormalWindow(0, root_window(), NULL);
   window->SetBounds(gfx::Rect(0, 0, 400, 400));
   EXPECT_EQ(child_windows + 1, root_window()->children().size());
 
   WindowSliderDeleteOwnerOnComplete slider_delegate(window);
   aura::test::EventGenerator generator(root_window());
 
   // Generate a horizontal overscroll.
   new WindowSlider(&slider_delegate, root_window(), window);
   generator.GestureScrollSequence(gfx::Point(10, 10),
                                   gfx::Point(180, 10),
                                   base::TimeDelta::FromMilliseconds(10),
                                   10);
   EXPECT_TRUE(slider_delegate.created_back_layer());
+  EXPECT_TRUE(slider_delegate.slide_completing());
   EXPECT_TRUE(slider_delegate.slide_completed());
   EXPECT_FALSE(slider_delegate.created_front_layer());
   EXPECT_FALSE(slider_delegate.slide_aborted());
   EXPECT_TRUE(slider_delegate.slider_destroyed());
 
   // Destroying the slider would have destroyed |window| too. So |window| should
   // not need to be destroyed here.
   EXPECT_EQ(child_windows, root_window()->children().size());
 }
 
+// Test the scenario when two swipe gesture occur quickly one after another so
+// that the second swipe occurs while the transition animation triggered by the
+// first swipe is in progress.
+// The second swipe is supposed to instantly complete the animation caused by
+// the first swipe, ask the delegate to create a new layer, and animate it.
+TEST_F(WindowSliderTest, SwipeDuringSwipeAnimation) {
+  scoped_ptr<aura::Window> window(CreateNormalWindow(0, root_window(), NULL));
+  window->SetBounds(gfx::Rect(0, 0, 400, 400));
+  WindowSliderDelegateTest slider_delegate;
+  new WindowSlider(&slider_delegate, root_window(), window.get());
+
+  ui::ScopedAnimationDurationScaleMode normal_duration_(
+      ui::ScopedAnimationDurationScaleMode::NORMAL_DURATION);
+  ui::LayerAnimator* animator = window->layer()->GetAnimator();
+  gfx::AnimationContainerElement* element = animator;
+  animator->set_disable_timer_for_test(true);
+  ui::LayerAnimatorTestController test_controller(animator);
+
+  aura::test::EventGenerator generator(root_window());
+
+  // Swipe forward so that |window|'s layer is the one animating.
+  generator.GestureScrollSequence(
+      gfx::Point(10, 10),
+      gfx::Point(180, 10),
+      base::TimeDelta::FromMilliseconds(10),
+      2);
+  EXPECT_TRUE(slider_delegate.created_back_layer());
+  EXPECT_FALSE(slider_delegate.slide_aborted());
+  EXPECT_FALSE(slider_delegate.created_front_layer());
+  EXPECT_TRUE(slider_delegate.slide_completing());
+  EXPECT_FALSE(slider_delegate.slide_completed());
+  EXPECT_FALSE(slider_delegate.slider_destroyed());
+  ui::ScopedLayerAnimationSettings settings(animator);
+  base::TimeDelta duration = settings.GetTransitionDuration();
+  test_controller.StartThreadedAnimationsIfNeeded();
+  base::TimeTicks start_time1 =  gfx::FrameTime::Now();
+
+  element->Step(start_time1 + duration/2);
+  EXPECT_FALSE(slider_delegate.slide_completed());
+  slider_delegate.Reset();
+  // Generate another horizontal swipe while the animation from the previous
+  // swipe is in progress.
+  generator.GestureScrollSequence(
+      gfx::Point(10, 10),
+      gfx::Point(180, 10),
+      base::TimeDelta::FromMilliseconds(10),
+      2);
+  // Performing the second swipe should instantly complete the slide started
+  // by the first swipe and create a new layer.
+  EXPECT_TRUE(slider_delegate.created_back_layer());
+  EXPECT_FALSE(slider_delegate.slide_aborted());
+  EXPECT_FALSE(slider_delegate.created_front_layer());
+  EXPECT_TRUE(slider_delegate.slide_completing());
+  EXPECT_TRUE(slider_delegate.slide_completed());
+  EXPECT_FALSE(slider_delegate.slider_destroyed());
+  test_controller.StartThreadedAnimationsIfNeeded();
+  base::TimeTicks start_time2 =  gfx::FrameTime::Now();
+  slider_delegate.Reset();
+  element->Step(start_time2 + duration);
+  // The animation for the second slide should now be completed.
+  EXPECT_TRUE(slider_delegate.slide_completed());
+  slider_delegate.Reset();
+
+  window.reset();
+  EXPECT_TRUE(slider_delegate.slider_destroyed());
+}
+
 }  // namespace content