Framework-side of SurfaceView#getBitmap

Bug: 27708453

Change-Id: Ie6fd7eca522d3e6549d8af587c975fd7e6053649
diff --git a/libs/hwui/Android.mk b/libs/hwui/Android.mk
index 0606b0b..717a1e6 100644
--- a/libs/hwui/Android.mk
+++ b/libs/hwui/Android.mk
@@ -84,6 +84,7 @@
     Properties.cpp \
     PropertyValuesHolder.cpp \
     PropertyValuesAnimatorSet.cpp \
+    Readback.cpp \
     RenderBufferCache.cpp \
     RenderNode.cpp \
     RenderProperties.cpp \