Fix buffer damage for quad-buffer

Test: none
Change-Id: I4789d84945e381d67e96ef37554a161dbd0ab16c
diff --git a/libs/hwui/renderthread/CanvasContext.h b/libs/hwui/renderthread/CanvasContext.h
index 8a76d6b..6e3e43a 100644
--- a/libs/hwui/renderthread/CanvasContext.h
+++ b/libs/hwui/renderthread/CanvasContext.h
@@ -242,7 +242,8 @@
         nsecs_t queueDuration;
     };
 
-    RingBuffer<SwapHistory, 3> mSwapHistory;
+    // Need at least 4 because we do quad buffer. Add a 5th for good measure.
+    RingBuffer<SwapHistory, 5> mSwapHistory;
     int64_t mFrameNumber = -1;
 
     // last vsync for a dropped frame due to stuffed queue