Roll engine. (#16087)

Changes since last roll:
```
ec1e96864 Revert pub roll from recent dart roll. (#4904)
ac552fba4 Port flutter content handler to FIDL2. (#4903)
94cdd8103 Roll dart. (#4902)
af63732de Support `Path.addCircle` (#4783)
564c6a5a9 Add hint to use ninja with goma (#4894)
```
```
diff --git a/bin/internal/engine.version b/bin/internal/engine.version
index 23e7ff7..2139ee6 100644
--- a/bin/internal/engine.version
+++ b/bin/internal/engine.version
@@ -1 +1 @@
-9af82c5a1a79ae02477db13e721c8365f31a4840
+ec1e96864ac8649789e8b1074d344b26f777e755