don't kill surfaceflinger when system process dies

Change-Id: I2d3ed87b590f9ccea3fa4af41d92911de070b315
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index b49fa36..4712261 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -147,6 +147,7 @@
 class SurfaceFlinger :
         public BinderService<SurfaceFlinger>,
         public BnSurfaceComposer,
+        public IBinder::DeathRecipient,
         protected Thread
 {
 public:
@@ -193,6 +194,10 @@
     sp<Layer> getLayer(const sp<ISurface>& sur) const;
 
 private:
+    // DeathRecipient interface
+    virtual void binderDied(const wp<IBinder>& who);
+
+private:
     friend class Client;
     friend class LayerBase;
     friend class LayerBaseClient;