Teach JankTracker about new swap behaviors

Bug: 30440166

If we are using HWC2, there's a change in timing
when in triple buffering with the pipelined offsets.
This changes JankTracker to recognize that and silently
erase that from the total duration

Change-Id: Ib1fd4209070f17dbd2baed707c8cf73fb11c3cf2
diff --git a/libs/hwui/Android.mk b/libs/hwui/Android.mk
index c9d4af6..366ef71 100644
--- a/libs/hwui/Android.mk
+++ b/libs/hwui/Android.mk
@@ -113,6 +113,10 @@
     -DATRACE_TAG=ATRACE_TAG_VIEW -DLOG_TAG=\"OpenGLRenderer\" \
     -Wall -Wno-unused-parameter -Wunreachable-code -Werror
 
+ifeq ($(TARGET_USES_HWC2),true)
+    hwui_cflags += -DUSE_HWC2
+endif
+
 # GCC false-positives on this warning, and since we -Werror that's
 # a problem
 hwui_cflags += -Wno-free-nonheap-object