Add a LayerScreenshot

A LayerScreenshot is a special type of layer that contains a screenshot of
the screen acquired when its created. It works just like LayerDim.

Make sure to call compositionComplete() after rendering into a FBO.

Bug: 5446982, 5467587, 5466259
Change-Id: I5d8a1b4c327f9973d950cd4f4c0bca7f62825cd4
diff --git a/services/surfaceflinger/Android.mk b/services/surfaceflinger/Android.mk
index dab0705..61a8358 100644
--- a/services/surfaceflinger/Android.mk
+++ b/services/surfaceflinger/Android.mk
@@ -5,6 +5,7 @@
     Layer.cpp 								\
     LayerBase.cpp 							\
     LayerDim.cpp 							\
+    LayerScreenshot.cpp						\
     DdmConnection.cpp						\
     DisplayHardware/DisplayHardware.cpp 	\
     DisplayHardware/DisplayHardwareBase.cpp \