Only enable hardware layers on visible workspace pages

Change-Id: Id82fc76d00a188556460d1a78388d46be56c9c4e
diff --git a/src/com/android/launcher2/CellLayout.java b/src/com/android/launcher2/CellLayout.java
index ccc842e..284db1b 100644
--- a/src/com/android/launcher2/CellLayout.java
+++ b/src/com/android/launcher2/CellLayout.java
@@ -302,7 +302,15 @@
     }
 
     public void enableHardwareLayers() {
-        mShortcutsAndWidgets.enableHardwareLayers();
+        mShortcutsAndWidgets.setLayerType(LAYER_TYPE_HARDWARE, null);
+    }
+
+    public void disableHardwareLayers() {
+        mShortcutsAndWidgets.setLayerType(LAYER_TYPE_NONE, null);
+    }
+
+    public void buildHardwareLayer() {
+        mShortcutsAndWidgets.buildLayer();
     }
 
     public void setGridSize(int x, int y) {