improve SurfaceFlinger 'dumpsys' log

list the purgatory, which shows windows that have been closed,
but for which the client still has references.

Change-Id: I5168bb88cb328d5d77d71d0871deb9190f493126
diff --git a/services/surfaceflinger/LayerBase.h b/services/surfaceflinger/LayerBase.h
index f6c49fc..13af223 100644
--- a/services/surfaceflinger/LayerBase.h
+++ b/services/surfaceflinger/LayerBase.h
@@ -211,6 +211,7 @@
     
     /** always call base class first */
     virtual void dump(String8& result, char* scratch, size_t size) const;
+    virtual void shortDump(String8& result, char* scratch, size_t size) const;
 
 
     enum { // flags for doTransaction()
@@ -324,6 +325,7 @@
 
 protected:
     virtual void dump(String8& result, char* scratch, size_t size) const;
+    virtual void shortDump(String8& result, char* scratch, size_t size) const;
 
 private:
     mutable Mutex mLock;