Pass sp<Fence>s around instead of file descriptors

Change-Id: Iac70584a2207940730e8f803a543e4e9a4000c47
diff --git a/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.h b/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.h
index 85a7a87..1347680 100644
--- a/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.h
+++ b/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.h
@@ -58,7 +58,7 @@
 
     virtual status_t compositionComplete();
     virtual status_t advanceFrame();
-    virtual void onFrameCommitted(int fenceFd);
+    virtual void onFrameCommitted(const sp<Fence>& fence);
     virtual void dump(String8& result) const;
 
 private: