Fixes in codegen and test script

test/codegen/expect/try_catch.js

Index: test/codegen/expect/try_catch.js
diff --git a/test/codegen/expect/try_catch.js b/test/codegen/expect/try_catch.js
new file mode 100644
index 0000000000000000000000000000000000000000..9ad17ef3a632d4cf824bc6822f71f2858da271ae
--- /dev/null
+++ b/test/codegen/expect/try_catch.js
@@ -0,0 +1,21 @@
+var try_catch;
+(function(exports) {
+  'use strict';
+  // Function main: () → dynamic
+  function main() {
+    try {
+      throw "hi there";
+    } catch ($e) {
+      if (dart.is($e, core.String)) {
+        let e = $e;
+        let t = dart.stackTrace(e);
+      }
+      let e = $e;
+      let t = dart.stackTrace(e);
+      throw e;
+    }
+
+  }
+  // Exports:
+  exports.main = main;
+})(try_catch || (try_catch = {}));