Removign optimations in onDestroy

> Workspace is still being held at
   Launcher > DragLayer > DragController > DragListeners
> The activity is not GCed immediately whith/without this optimization
> No momory/GPU change with/without this optimization

Change-Id: I9466ed47adbac717954d1998951937b04bc4cfd5

src/com/android/launcher3/Launcher.java

@@ -1987,13 +1987,11 @@ public class Launcher extends Activity
         mWorkspace.removeCallbacks(mBuildLayersRunnable);
 
         // Stop callbacks from LauncherModel
-        LauncherAppState app = (LauncherAppState.getInstance());
-
         // It's possible to receive onDestroy after a new Launcher activity has
         // been created. In this case, don't interfere with the new Launcher.
         if (mModel.isCurrentCallbacks(this)) {
             mModel.stopLoader();
-            app.setLauncher(null);
+            LauncherAppState.getInstance().setLauncher(null);
         }
 
         try {
@@ -2009,12 +2007,6 @@ public class Launcher extends Activity
 
         unregisterReceiver(mCloseSystemDialogsReceiver);
 
-        mDragLayer.clearAllResizeFrames();
-        ((ViewGroup) mWorkspace.getParent()).removeAllViews();
-        mWorkspace.removeAllWorkspaceScreens();
-        mWorkspace = null;
-        mDragController = null;
-
         LauncherAnimUtils.onDestroyActivity();
 
         if (mLauncherCallbacks != null) {