Hide scroll arrows from Alt+Tab UI

Recent recommendation from UX was to hide scroll arrows from
Alt+Tab UI, as the primary use case is keyboard focused.

Bug: 397975686
Flag: com.android.launcher3.taskbar_overflow
Test: Verify that arrows are visible when KQS is opened from taskbar
      overflow button (when there's enough items to make KQS
      scrollable), and invisible when triggered using Alt+Tab shortcut.
Change-Id: Iaab234aca94d262b8151a680a08d10d6b39054ed

quickstep/src/com/android/launcher3/taskbar/KeyboardQuickSwitchView.java

@@ -47,7 +47,6 @@ import androidx.constraintlayout.widget.ConstraintLayout;
 
 import com.android.app.animation.Interpolators;
 import com.android.internal.jank.Cuj;
-import com.android.launcher3.Flags;
 import com.android.launcher3.R;
 import com.android.launcher3.Utilities;
 import com.android.launcher3.anim.AnimatedFloat;
@@ -180,17 +179,6 @@ public class KeyboardQuickSwitchView extends ConstraintLayout {
 
         mIsRtl = Utilities.isRtl(resources);
 
-        if (Flags.taskbarOverflow()) {
-            initializeScrollArrows();
-
-            if (mIsRtl) {
-                mStartScrollArrow.setContentDescription(
-                        resources.getString(R.string.quick_switch_scroll_arrow_right));
-                mEndScrollArrow.setContentDescription(
-                        resources.getString(R.string.quick_switch_scroll_arrow_left));
-            }
-        }
-
         TypefaceUtils.setTypeface(
                 mNoRecentItemsPane.findViewById(R.id.no_recent_items_text),
                 FontFamily.GSF_LABEL_LARGE);
@@ -359,9 +347,21 @@ public class KeyboardQuickSwitchView extends ConstraintLayout {
                 });
     }
 
-    private void initializeScrollArrows() {
+
+    void enableScrollArrowSupport() {
+        if (mSupportsScrollArrows) {
+            return;
+        }
         mSupportsScrollArrows = true;
 
+        if (mIsRtl) {
+            mStartScrollArrow.setContentDescription(
+                    getResources().getString(R.string.quick_switch_scroll_arrow_right));
+            mEndScrollArrow.setContentDescription(
+                    getResources().getString(R.string.quick_switch_scroll_arrow_left));
+        }
+
+
         mStartScrollArrow.setOnClickListener(new OnClickListener() {
             @Override
             public void onClick(View v) {

quickstep/src/com/android/launcher3/taskbar/KeyboardQuickSwitchViewController.java

@@ -34,6 +34,7 @@ import androidx.annotation.Nullable;
 
 import com.android.internal.jank.Cuj;
 import com.android.launcher3.DeviceProfile;
+import com.android.launcher3.Flags;
 import com.android.launcher3.R;
 import com.android.launcher3.Utilities;
 import com.android.launcher3.anim.AnimatorListeners;
@@ -119,6 +120,10 @@ public class KeyboardQuickSwitchViewController {
         mWasDesktopTaskFilteredOut = wasDesktopTaskFilteredOut;
         mWasOpenedFromTaskbar = wasOpenedFromTaskbar;
 
+        if (Flags.taskbarOverflow() && wasOpenedFromTaskbar) {
+            mKeyboardQuickSwitchView.enableScrollArrowSupport();
+        }
+
         mKeyboardQuickSwitchView.applyLoadPlan(
                 mOverlayContext,
                 tasks,