Update for cleanups in hwc interface

Change-Id: I363fd8b085167a1af6c14b68012bda5c62bfe59f
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.h b/services/surfaceflinger/DisplayHardware/HWComposer.h
index 8080d3b..d15c6f4 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.h
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.h
@@ -229,8 +229,9 @@
 
     struct cb_context;
 
-    static void hook_invalidate(struct hwc_procs* procs);
-    static void hook_vsync(struct hwc_procs* procs, int dpy, int64_t timestamp);
+    static void hook_invalidate(const struct hwc_procs* procs);
+    static void hook_vsync(const struct hwc_procs* procs, int dpy,
+            int64_t timestamp);
 
     inline void invalidate();
     inline void vsync(int dpy, int64_t timestamp);