Add/fix/cleanup type inference for throw and rethrow.

pkg/front_end/testcases/inference/infer_rethrow.dart.direct.expect

Index: pkg/front_end/testcases/inference/infer_rethrow.dart.direct.expect
diff --git a/pkg/front_end/testcases/inference/infer_rethrow.dart.direct.expect b/pkg/front_end/testcases/inference/infer_rethrow.dart.direct.expect
new file mode 100644
index 0000000000000000000000000000000000000000..5ecaf4314857bbfc611a50e9cbd7fffb86b63ff4
--- /dev/null
+++ b/pkg/front_end/testcases/inference/infer_rethrow.dart.direct.expect
@@ -0,0 +1,13 @@
+library test;
+import self as self;
+
+static method test(() → dynamic f, () → dynamic g) → dynamic {
+  try {
+    f.call();
+  }
+  on dynamic catch(final dynamic _) {
+    g.call();
+    rethrow;
+  }
+}
+static method main() → dynamic {}