Fix broken build for more tests

Change-Id: I7bdd12a833233724805d01d993541ee05caa9bf6
diff --git a/libs/gui/tests/IGraphicBufferProducer_test.cpp b/libs/gui/tests/IGraphicBufferProducer_test.cpp
index 4d38ff5..c2653c2 100644
--- a/libs/gui/tests/IGraphicBufferProducer_test.cpp
+++ b/libs/gui/tests/IGraphicBufferProducer_test.cpp
@@ -66,6 +66,7 @@
 struct DummyConsumer : public BnConsumerListener {
     virtual void onFrameAvailable() {}
     virtual void onBuffersReleased() {}
+    virtual void onSidebandStreamChanged() {}
 };
 
 class IGraphicBufferProducerTest : public ::testing::Test {