Clean up fully rolled out flag enable_desktop_task_alpha_animation

Flag: EXEMPT removing flag
Bug: 409605077
Test: None; flag is already fully rolled out
Change-Id: I92c8520ce1f924104453be7e969bd6095d612717

aconfig/launcher.aconfig

@@ -355,16 +355,6 @@ flag {
     bug: "358673724"
 }
 
-flag {
-    name: "enable_desktop_task_alpha_animation"
-    namespace: "launcher"
-    description: "Enables the animation of the desktop task's background view"
-    bug: "320307666"
-    metadata {
-      purpose: PURPOSE_BUGFIX
-    }
-}
-
 flag {
     name: "ignore_three_finger_trackpad_for_nav_handle_long_press"
     namespace: "launcher"
@@ -706,4 +696,4 @@ flag {
   metadata {
     purpose: PURPOSE_BUGFIX
   }
-}
+}

quickstep/src/com/android/quickstep/views/RecentsView.java

@@ -37,9 +37,7 @@ import static com.android.launcher3.AbstractFloatingView.TYPE_REBIND_SAFE;
 import static com.android.launcher3.BaseActivity.STATE_HANDLER_INVISIBILITY_FLAGS;
 import static com.android.launcher3.Flags.enableAdditionalHomeAnimations;
 import static com.android.launcher3.Flags.enableDesktopExplodedView;
-import static com.android.launcher3.Flags.enableDesktopTaskAlphaAnimation;
 import static com.android.launcher3.Flags.enableExpressiveDismissTaskMotion;
-import static com.android.launcher3.util.OverviewReleaseFlags.enableGridOnlyOverview;
 import static com.android.launcher3.Flags.enableLargeDesktopWindowingTile;
 import static com.android.launcher3.Flags.enableOverviewBackgroundWallpaperBlur;
 import static com.android.launcher3.Flags.enableRefactorTaskThumbnail;
@@ -64,6 +62,7 @@ import static com.android.launcher3.touch.PagedOrientationHandler.CANVAS_TRANSLA
 import static com.android.launcher3.util.Executors.MAIN_EXECUTOR;
 import static com.android.launcher3.util.Executors.UI_HELPER_EXECUTOR;
 import static com.android.launcher3.util.MultiPropertyFactory.MULTI_PROPERTY_VALUE;
+import static com.android.launcher3.util.OverviewReleaseFlags.enableGridOnlyOverview;
 import static com.android.launcher3.util.SystemUiController.UI_STATE_FULLSCREEN_TASK;
 import static com.android.quickstep.BaseContainerInterface.getTaskDimension;
 import static com.android.quickstep.TaskUtils.checkCurrentOrManagedUserId;
@@ -2919,7 +2918,7 @@ public abstract class RecentsView<
      * Returns whether the running task's attach alpha should be updated during the attach animation
      */
     public boolean shouldUpdateRunningTaskAlpha() {
-        return enableDesktopTaskAlphaAnimation() && getRunningTaskView() instanceof DesktopTaskView;
+        return getRunningTaskView() instanceof DesktopTaskView;
     }
 
     private boolean isGestureActive() {
@@ -4956,9 +4955,8 @@ public abstract class RecentsView<
                     : showAsGrid
                             ? gridOffsetSize
                             : i < modalMidpoint ? modalLeftOffsetSize : modalRightOffsetSize;
-            boolean skipTranslationOffset = enableDesktopTaskAlphaAnimation()
-                    && i == getRunningTaskIndex()
-                    && child instanceof DesktopTaskView;
+            boolean skipTranslationOffset =
+                    i == getRunningTaskIndex() && child instanceof DesktopTaskView;
             float totalTranslationX = (skipTranslationOffset ? 0f : translation) + modalTranslation
                     + carouselHiddenOffsetSize;
             if (child instanceof TaskView taskView) {