Dart SDK roll for 2018-10-23 (#23439)

diff --git a/bin/internal/engine.version b/bin/internal/engine.version
index 5ad8958..5ef6298 100644
--- a/bin/internal/engine.version
+++ b/bin/internal/engine.version
@@ -1 +1 @@
-2586e941225726f0429b9e67f4d9b6ab404d7b1e
+26e8840de5d6fe801378301dd36d54c92b25bd3b