Fix a couple of drag and drop issues from transient taskbar

- Don't stash until drag ends, but immediately stash at that point
  (regardless of success or failure, though failure will animate to the
  original icon before stashing)
- Send transient taskbar's bounds to WM Shell via intent extra such that
  they ignore drag events in that region

Test: manual in persistent and transient taskbar
Bug: 269814838
Fixes: 268526633
Fixes: 259645384
Change-Id: I5ded3998046f259ed6e79cb4ed765ad7b0c72e45

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

@@ -20,6 +20,7 @@ import static android.view.KeyEvent.KEYCODE_BACK;
 
 import android.content.Context;
 import android.graphics.Canvas;
+import android.graphics.RectF;
 import android.util.AttributeSet;
 import android.view.KeyEvent;
 import android.view.MotionEvent;
@@ -183,6 +184,11 @@ public class TaskbarDragLayer extends BaseDragLayer<TaskbarActivityContext> {
         invalidate();
     }
 
+    /** Returns the bounds in DragLayer coordinates of where the transient background was drawn. */
+    protected RectF getLastDrawnTransientRect() {
+        return mBackgroundRenderer.getLastDrawnTransientRect();
+    }
+
     @Override
     public boolean dispatchTouchEvent(MotionEvent ev) {
         TestLogging.recordMotionEvent(TestProtocol.SEQUENCE_MAIN, "Touch event", ev);