Add support for sending VSYNC events to the framework

use gui/DisplayEvent to receive the events. Events are
dispatched through a unix pipe, so the API is compatible
with utils/Looper. see gui/DisplayEvent.h for more info.

Bug: 1475048
Change-Id: Ia720f64d1b950328b47b22c6a86042e481d35f09
diff --git a/libs/gui/Android.mk b/libs/gui/Android.mk
index b7e3ee3..b8be67d 100644
--- a/libs/gui/Android.mk
+++ b/libs/gui/Android.mk
@@ -3,6 +3,8 @@
 
 LOCAL_SRC_FILES:= \
 	BitTube.cpp \
+	DisplayEventReceiver.cpp \
+	IDisplayEventConnection.cpp \
 	ISensorEventConnection.cpp \
 	ISensorServer.cpp \
 	ISurfaceTexture.cpp \