fix [2712278] The preview buffer left some black borders in left and bottom edges

we were incorrectly flagging push_buffer surfaces as invalid

Change-Id: I4dfd4ffbbe8a71f7e23e835db8d71966416c29bb
diff --git a/include/private/surfaceflinger/SharedBufferStack.h b/include/private/surfaceflinger/SharedBufferStack.h
index ea8391d..b859e78 100644
--- a/include/private/surfaceflinger/SharedBufferStack.h
+++ b/include/private/surfaceflinger/SharedBufferStack.h
@@ -159,7 +159,6 @@
     SharedBufferBase(SharedClient* sharedClient, int surface,
             int32_t identity);
     ~SharedBufferBase();
-    uint32_t getIdentity();
     status_t getStatus() const;
     size_t getFrontBuffer() const;
     String8 dump(char const* prefix) const;