Sanity check screenId before persisting ItemInfo.

Bug: 13447571
Change-Id: I014dcf1eb313c2312953716fb53e542caaeb285b

src/com/android/launcher3/ItemInfo.java

@@ -140,6 +140,11 @@ public class ItemInfo {
         values.put(LauncherSettings.Favorites.CELLY, cellY);
         values.put(LauncherSettings.Favorites.SPANX, spanX);
         values.put(LauncherSettings.Favorites.SPANY, spanY);
+
+        if (screenId == Workspace.EXTRA_EMPTY_SCREEN_ID) {
+            // We should never persist an item on the extra empty screen.
+            throw new RuntimeException("Screen id should not be EXTRA_EMPTY_SCREEN_ID");
+        }
     }
 
     void updateValuesWithCoordinates(ContentValues values, int cellX, int cellY) {

src/com/android/launcher3/Workspace.java

@@ -126,7 +126,7 @@ public class Workspace extends SmoothPagedView
     private static boolean sAccessibilityEnabled;
 
     // The screen id used for the empty screen always present to the right.
-    private final static long EXTRA_EMPTY_SCREEN_ID = -201;
+    final static long EXTRA_EMPTY_SCREEN_ID = -201;
     private final static long CUSTOM_CONTENT_SCREEN_ID = -301;
 
     private HashMap<Long, CellLayout> mWorkspaceScreens = new HashMap<Long, CellLayout>();