Fixing page background not displayed when dragging from all apps

> Adding empty page synchronously, instead of waiting for a frame
> Changing launcher state from widgets screen in the same frame, similar to all apps
> Removing DragEnforcer, and moving that logic in side the workspace, disabled by a flag
> Using first page to get page bounds in drag layer, as last page may not have been measured

Change-Id: I172ba4e5ce44648ac55402d49994542c6e10f101

src/com/android/launcher3/allapps/AllAppsContainerView.java

@@ -447,7 +447,6 @@ public class AllAppsContainerView extends BaseContainerView implements DragSourc
     @Override
     protected void onFixedBoundsUpdated() {
         // Update the number of items in the grid
-        LauncherAppState app = LauncherAppState.getInstance();
         DeviceProfile grid = mLauncher.getDeviceProfile();
         if (grid.updateAppsViewNumCols(getContext().getResources(), mFixedBounds.width())) {
             mNumAppsPerRow = grid.allAppsNumCols;