Cros: Reset mask layer after scroll ended.

We assumed that TransitionEnded() would happen almost every time we
interact with the page switcher, but some edge cases don't animate a
transition, particularly after a scroll. For this edge cases, we delete
the mask layer when ScrollEnded(). We also check if the mask layer still
exists when TransitionEnded() to reset it if needed (i.e. when no scroll
is involved in page switching)

Bug: 1049275
Change-Id: I8bdebd6a0b0776f202ac5ee6af8990f41bb22ea4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2070795Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Commit-Queue: Ana Salazar <anasalazar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744315}

ash/app_list/views/apps_grid_view.cc

@@ -2858,7 +2858,8 @@ void AppsGridView::TransitionEnded() {
         compositor->refresh_rate(), IsTabletMode());
   }
   // Gradient mask is no longer necessary once transition is finished.
-  layer()->SetMaskLayer(nullptr);
+  if (layer()->layer_mask_layer())
+    layer()->SetMaskLayer(nullptr);
 }
 
 void AppsGridView::ScrollStarted() {
@@ -2879,8 +2880,9 @@ void AppsGridView::ScrollStarted() {
 void AppsGridView::ScrollEnded() {
   // Scroll can end without triggering state animation.
   presentation_time_recorder_.reset();
-  // No need to reset the mask because transition will happen in almost all
-  // cases.
+  // Need to reset the mask because transition will not happen in some
+  // cases. (See https://crbug.com/1049275)
+  layer()->SetMaskLayer(nullptr);
 }
 
 void AppsGridView::OnAppListModelStatusChanged() {

ash/app_list/views/apps_grid_view_unittest.cc

@@ -1859,6 +1859,59 @@ TEST_P(AppsGridViewTabletTest, Basic) {
       1);
 }
 
+// Make sure that a folder icon resets background blur after scrolling the apps
+// grid without completing any transition (See https://crbug.com/1049275). The
+// background blur is masked by the apps grid's layer mask.
+TEST_F(AppsGridViewTabletTest, EnsureBlurAfterScrollingWithoutTransition) {
+  // Create a folder with 2 apps. Then add apps until a second page is created.
+  model_->CreateAndPopulateFolderWithApps(2);
+  model_->PopulateApps(GetTilesPerPage(0));
+  EXPECT_EQ(2, GetPaginationModel()->total_pages());
+
+  gfx::Point apps_grid_view_origin =
+      apps_grid_view_->GetBoundsInScreen().origin();
+  ui::GestureEvent scroll_begin(
+      apps_grid_view_origin.x(), apps_grid_view_origin.y(), 0,
+      base::TimeTicks(),
+      ui::GestureEventDetails(ui::ET_GESTURE_SCROLL_BEGIN, 0, -1));
+  ui::GestureEvent scroll_update_upwards(
+      apps_grid_view_origin.x(), apps_grid_view_origin.y(), 0,
+      base::TimeTicks(),
+      ui::GestureEventDetails(ui::ET_GESTURE_SCROLL_UPDATE, 0, -10));
+  ui::GestureEvent scroll_update_downwards(
+      apps_grid_view_origin.x(), apps_grid_view_origin.y(), 0,
+      base::TimeTicks(),
+      ui::GestureEventDetails(ui::ET_GESTURE_SCROLL_UPDATE, 0, 15));
+  ui::GestureEvent scroll_end(
+      apps_grid_view_origin.x(), apps_grid_view_origin.y(), 0,
+      base::TimeTicks(), ui::GestureEventDetails(ui::ET_GESTURE_SCROLL_END));
+
+  AppListItemView* folder_view = GetItemViewAt(0);
+  ASSERT_TRUE(folder_view->is_folder());
+  ASSERT_FALSE(apps_grid_view_->layer()->layer_mask_layer());
+
+  // On the first page drag upwards, there should not be a page switch and the
+  // layer mask should make the folder lose blur.
+  ASSERT_EQ(0, GetPaginationModel()->selected_page());
+  apps_grid_view_->OnGestureEvent(&scroll_begin);
+  EXPECT_TRUE(scroll_begin.handled());
+  apps_grid_view_->OnGestureEvent(&scroll_update_upwards);
+  EXPECT_TRUE(scroll_update_upwards.handled());
+
+  ASSERT_EQ(0, GetPaginationModel()->selected_page());
+  ASSERT_TRUE(apps_grid_view_->layer()->layer_mask_layer());
+
+  // Continue drag, now switching directions and release. There shouldn't be any
+  // transition and the mask layer should've been reset.
+  apps_grid_view_->OnGestureEvent(&scroll_update_downwards);
+  EXPECT_TRUE(scroll_update_downwards.handled());
+  apps_grid_view_->OnGestureEvent(&scroll_end);
+  EXPECT_TRUE(scroll_end.handled());
+
+  EXPECT_FALSE(GetPaginationModel()->has_transition());
+  EXPECT_FALSE(apps_grid_view_->layer()->layer_mask_layer());
+}
+
 INSTANTIATE_TEST_SUITE_P(All, AppsGridViewTabletTest, testing::Bool());
 
 // Test various dragging behaviors only allowed when apps grid gap (part of