Roll src/third_party/dart a8f433820b..7799f424f4 (3 commits)

dart-lang/sdk@7799f424f4 [CFE] Encapsulate int operations in separate classes for VM and JS
dart-lang/sdk@eb1a375749 [CFE] Consolidate double special cases for == and identical.
dart-lang/sdk@7b60ae1a0d [cfe] Fix infer expression

DEPS

@@ -34,7 +34,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/master/DEPS.
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': 'a8f433820b0836f85a92eb17562bdf71c339c93a',
+  'dart_revision': '7799f424f4a2ba35ce9f64593e5e593a1a553f67',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py