Add support for system shortcuts in popup container

- Currently the system shortcuts are just widgets and app info
- As shortcuts, they live in ShortcutsItemView
- They are populated either as icons only (if there are deep
  shortcuts) or as icons + text
- Widgets are disabled until binding them is complete (we request for
  them to be bound on long-press now). We should revisit this.

Bug: 34940468
Change-Id: Ia51d002c3b3ede87658bdab57abfc3eeca1ed242

src/com/android/launcher3/AbstractFloatingView.java

@@ -92,6 +92,9 @@ public abstract class AbstractFloatingView extends LinearLayout {
         return mIsOpen;
     }
 
+    protected void onWidgetsBound() {
+    }
+
     protected abstract boolean isOfType(@FloatingViewType int type);
 
     protected static <T extends AbstractFloatingView> T getOpenView(