Implement type inference for conventional for-loops.

pkg/front_end/testcases/inference/infer_types_on_loop_indices_for_loop_with_inference.dart.strong.expect

Index: pkg/front_end/testcases/inference/infer_types_on_loop_indices_for_loop_with_inference.dart.strong.expect
diff --git a/pkg/front_end/testcases/inference/infer_types_on_loop_indices_for_loop_with_inference.dart.strong.expect b/pkg/front_end/testcases/inference/infer_types_on_loop_indices_for_loop_with_inference.dart.strong.expect
new file mode 100644
index 0000000000000000000000000000000000000000..e3d4755ab297ac21b809dd5353b6814a21a2d30d
--- /dev/null
+++ b/pkg/front_end/testcases/inference/infer_types_on_loop_indices_for_loop_with_inference.dart.strong.expect
@@ -0,0 +1,10 @@
+library test;
+import self as self;
+import "dart:core" as core;
+
+static method test() → dynamic {
+  for (core::int i = 0; i.{core::num::<}(10); i = i.{core::num::+}(1)) {
+    core::int j = i.{core::num::+}(1);
+  }
+}
+static method main() → dynamic {}