Add a way for wallpapers to know the delta between virtual screens.
diff --git a/core/java/android/view/IWindow.aidl b/core/java/android/view/IWindow.aidl
index 6bfc8b5..71302cb 100644
--- a/core/java/android/view/IWindow.aidl
+++ b/core/java/android/view/IWindow.aidl
@@ -62,7 +62,7 @@
     /**
      * Called for wallpaper windows when their offsets change.
      */
-    void dispatchWallpaperOffsets(float x, float y, boolean sync);
+    void dispatchWallpaperOffsets(float x, float y, float xStep, float yStep, boolean sync);
     
     void dispatchWallpaperCommand(String action, int x, int y,
             int z, in Bundle extras, boolean sync);