Triple buffer SurfaceFlinger

This change sets SurfaceFlinger to use triple buffering for its GLES
composition.

Bug: 7283132
Change-Id: I21fda29018df6bf48c4bfa53d37787cb3248fb4a
diff --git a/BoardConfig.mk b/BoardConfig.mk
index 3c96b19..3dafbc0 100755
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -49,6 +49,7 @@
 #BOARD_USES_HGL := true
 #BOARD_USES_OVERLAY := true
 USE_OPENGL_RENDERER := true
+NUM_FRAMEBUFFER_SURFACE_BUFFERS := 3
 
 TARGET_USERIMAGES_USE_EXT4 := true
 BOARD_SYSTEMIMAGE_PARTITION_SIZE := 685768704