SF: Abstract out buffer queue creation

Modifies SurfaceFlinger so that the type of the buffer queue
producer/consumer pair produced for framebuffers can be changed at
runtime.

Test: Builds
Bug: None
Change-Id: If108059c43e5c0d03de9645966d9b8eca2b9ed16
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 08c4a5e..37024ae 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -87,6 +87,8 @@
 class DisplayEventConnection;
 class EventControlThread;
 class EventThread;
+class IGraphicBufferConsumer;
+class IGraphicBufferProducer;
 class InjectVSyncSource;
 class Layer;
 class Surface;
@@ -822,6 +824,12 @@
     float mSaturation = 1.0f;
     bool mForceNativeColorMode = false;
 
+    using CreateBufferQueueFunction =
+            std::function<void(sp<IGraphicBufferProducer>* /* outProducer */,
+                               sp<IGraphicBufferConsumer>* /* outConsumer */,
+                               bool /* consumerIsSurfaceFlinger */)>;
+    CreateBufferQueueFunction mCreateBufferQueue;
+
     SurfaceFlingerBE mBE;
 };
 }; // namespace android