Add a render buffer cache to reuse stencil buffers
Bug #7146141

This new cache is used in a similar way to LayerCache. It helps
reuse already allocated stencil buffers and thus avoid churning
memory on every frame.

Change-Id: I19551d72da52c40039e65904563600e492c8b193
diff --git a/libs/hwui/Android.mk b/libs/hwui/Android.mk
index 2111a56..d533fa0 100644
--- a/libs/hwui/Android.mk
+++ b/libs/hwui/Android.mk
@@ -28,6 +28,7 @@
 		PathTessellator.cpp \
 		Program.cpp \
 		ProgramCache.cpp \
+		RenderBufferCache.cpp \
 		ResourceCache.cpp \
 		ShapeCache.cpp \
 		SkiaColorFilter.cpp \