Version 3.8.0-278.3.beta

Change-Id: Ie02c0aa143d5aca4ebfabb7b1c8e4118716dbbe4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/425301
Reviewed-by: Alexander Thomas <athom@google.com>
Commit-Queue: Ivan Inozemtsev <iinozemtsev@google.com>
Commit-Queue: Alexander Thomas <athom@google.com>
Auto-Submit: Ivan Inozemtsev <iinozemtsev@google.com>
diff --git a/tools/VERSION b/tools/VERSION
index 30bcebe..9b190d3 100644
--- a/tools/VERSION
+++ b/tools/VERSION
@@ -28,4 +28,4 @@
 MINOR 8
 PATCH 0
 PRERELEASE 278
-PRERELEASE_PATCH 2
+PRERELEASE_PATCH 3