wallpaper: Re-enable cross fade wallpaper blur for overview.

It was disabled because causing a regression. Switches it up a bit to
instead create a smaller widget which draws its own blurred
WallpaperView, which is then scaled before being faded in. The widget
is kept alive for the duration of overview.

Test: manual
Bug: 1012829
Change-Id: I0b132a52c2ea26ffddd6b6537ab4062b80960e7f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1876873
Commit-Queue: Sammie Quon <sammiequon@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711321}

ash/public/cpp/ash_features.cc

@@ -57,7 +57,7 @@ const base::Feature kNotificationScrollBar{"NotificationScrollBar",
                                            base::FEATURE_DISABLED_BY_DEFAULT};
 
 const base::Feature kOverviewCrossFadeWallpaperBlur{
-    "OverviewCrossFadeWallpaperBlur", base::FEATURE_DISABLED_BY_DEFAULT};
+    "OverviewCrossFadeWallpaperBlur", base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kPipRoundedCorners{"PipRoundedCorners",
                                        base::FEATURE_DISABLED_BY_DEFAULT};

ash/wm/overview/overview_item.cc

@@ -444,14 +444,18 @@ void OverviewItem::SetBounds(const gfx::RectF& target_bounds,
           PerformItemSpawnedAnimation(item_widget_->GetNativeWindow(),
                                       gfx::Transform{});
         } else {
-          FadeInWidgetAndMaybeSlideOnEnter(
-              item_widget_.get(),
-              (new_animation_type ==
-               OVERVIEW_ANIMATION_ENTER_FROM_HOME_LAUNCHER)
-                  ? new_animation_type
-                  : OVERVIEW_ANIMATION_ENTER_OVERVIEW_MODE_FADE_IN,
-              /*slide=*/false,
-              /*observe=*/true);
+          // Items that are slide in already have their slide in animations
+          // handled in |SlideWindowIn|.
+          const bool slide_in =
+              overview_session_->enter_exit_overview_type() ==
+              OverviewSession::EnterExitOverviewType::kSlideInEnter;
+          if (!slide_in) {
+            FadeInWidgetAndMaybeSlideOnEnter(
+                item_widget_.get(),
+                OVERVIEW_ANIMATION_ENTER_OVERVIEW_MODE_FADE_IN,
+                /*slide=*/false,
+                /*observe=*/true);
+          }
 
           // Update the item header visibility immediately if entering from home
           // launcher.

ash/wm/overview/overview_wallpaper_controller.cc

@@ -270,8 +270,8 @@ void OverviewWallpaperController::OnBlurChangeCrossFade(
 
     ui::Layer* original_layer = wallpaper_window->layer();
     original_layer->GetAnimator()->StopAnimating();
-    original_layer->SetLayerBlur(should_blur ? kWallpaperBlurSigma
-                                             : kWallpaperClearBlurSigma);
+    wallpaper_widget_controller->wallpaper_view()->RepaintBlurAndOpacity(
+        should_blur ? kWallpaperBlurSigma : kWallpaperClearBlurSigma, 1.f);
     original_layer->SetOpacity(should_blur ? 0.f : 1.f);
 
     ui::Layer* copy_layer = copy_layer_tree ? copy_layer_tree->root() : nullptr;