Disable hardware layers for drag views

Also, avoiding allocating paint object every time we swipe
diff --git a/src/com/android/launcher2/CellLayout.java b/src/com/android/launcher2/CellLayout.java
index 284db1b..34c290a 100644
--- a/src/com/android/launcher2/CellLayout.java
+++ b/src/com/android/launcher2/CellLayout.java
@@ -159,6 +159,7 @@
 
     private final static PorterDuffXfermode sAddBlendMode =
             new PorterDuffXfermode(PorterDuff.Mode.ADD);
+    private final static Paint sPaint = new Paint();
 
     public CellLayout(Context context) {
         this(context, null);
@@ -302,11 +303,11 @@
     }
 
     public void enableHardwareLayers() {
-        mShortcutsAndWidgets.setLayerType(LAYER_TYPE_HARDWARE, null);
+        mShortcutsAndWidgets.setLayerType(LAYER_TYPE_HARDWARE, sPaint);
     }
 
     public void disableHardwareLayers() {
-        mShortcutsAndWidgets.setLayerType(LAYER_TYPE_NONE, null);
+        mShortcutsAndWidgets.setLayerType(LAYER_TYPE_NONE, sPaint);
     }
 
     public void buildHardwareLayer() {