Pass sp<Fence>s around instead of file descriptors

Change-Id: Iac70584a2207940730e8f803a543e4e9a4000c47
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.h b/services/surfaceflinger/DisplayHardware/HWComposer.h
index fdbd2d9..346526a 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.h
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.h
@@ -114,7 +114,7 @@
 
     // get the releaseFence file descriptor for a display's framebuffer layer.
     // the release fence is only valid after commit()
-    int getAndResetReleaseFenceFd(int32_t id);
+    sp<Fence> getAndResetReleaseFence(int32_t id);
 
     // needed forward declarations
     class LayerListIterator;
@@ -141,7 +141,7 @@
     public:
         virtual int32_t getCompositionType() const = 0;
         virtual uint32_t getHints() const = 0;
-        virtual int getAndResetReleaseFenceFd() = 0;
+        virtual sp<Fence> getAndResetReleaseFence() = 0;
         virtual void setDefaultState() = 0;
         virtual void setSkip(bool skip) = 0;
         virtual void setBlending(uint32_t blending) = 0;