Use invisible icon for POINTER_ICON_STYLE_NULL.

Change-Id: I10d35bdc4da4817d769eb164e6f15e4618670a05
diff --git a/libs/input/PointerController.h b/libs/input/PointerController.h
index 308ff12..24a1681 100644
--- a/libs/input/PointerController.h
+++ b/libs/input/PointerController.h
@@ -58,7 +58,8 @@
 
 public:
     virtual void loadPointerResources(PointerResources* outResources) = 0;
-    virtual void loadAdditionalMouseResources(std::map<int, SpriteIcon>* outResources) = 0;
+    virtual void loadAdditionalMouseResources(std::map<int32_t, SpriteIcon>* outResources) = 0;
+    virtual int32_t getDefaultPointerIconId() = 0;
 };