Add left widget panel to Launcher home when unfolded

Test: manual
Bug: 175939730
Change-Id: I9831e7fa95084db12953ec7cb2eb725e7549e01d

src/com/android/launcher3/model/ModelWriter.java

@@ -112,6 +112,13 @@ public class ModelWriter {
         }
     }
 
+    /**
+     * Sets the value that indicates if left widget panel is shown or not.
+     */
+    public void setLeftPanelShown(boolean value) {
+        mBgDataModel.isLeftPanelShown = value;
+    }
+
     private void checkItemInfoLocked(int itemId, ItemInfo item, StackTraceElement[] stackTrace) {
         ItemInfo modelItem = mBgDataModel.itemsIdMap.get(itemId);
         if (modelItem != null && item != modelItem) {