Fix two panel home folder opening display issue

Change the rect calculation logic that is used to
display an opening folder. If multiple panels are
displayed then we calculate the union of the pages.

Test: manual
Bug: 181962118
Change-Id: I504f22890115ceebc16d60929149fe634bf820d0
diff --git a/src/com/android/launcher3/Launcher.java b/src/com/android/launcher3/Launcher.java
index 8785fbc..5eba399 100644
--- a/src/com/android/launcher3/Launcher.java
+++ b/src/com/android/launcher3/Launcher.java
@@ -1781,9 +1781,7 @@
     @Override
     public Rect getFolderBoundingBox() {
         // We need to bound the folder to the currently visible workspace area
-        Rect folderBoundingBox = new Rect();
-        getWorkspace().getPageAreaRelativeToDragLayer(folderBoundingBox);
-        return folderBoundingBox;
+        return getWorkspace().getPageAreaRelativeToDragLayer();
     }
 
     @Override