[Autoroll] Looks like Flutter/Engine PRs now have tree checks

Bug: skia:8841
Change-Id: I76d0afdda36ae802ec0b83a2a12bab53a93ba62c
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/199486
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>
diff --git a/autoroll/config/skia-flutter.json b/autoroll/config/skia-flutter.json
index 41942d7..5fb9a0b 100644
--- a/autoroll/config/skia-flutter.json
+++ b/autoroll/config/skia-flutter.json
@@ -16,7 +16,11 @@
     "repoOwner": "flutter",
     "repoName": "engine",
     "checksNum": 4,
-    "checksWaitFor": []
+    "checksWaitFor": [
+      "windows-build",
+      "linux-build",
+      "mac-build"
+    ]
   },
   "githubDEPSRepoManager": {
     "childBranch": "master",