Check in codegen test expectations.

test/codegen/expect/corelib/throw_half_surrogate_pair_test_01_multi.js

Index: test/codegen/expect/corelib/throw_half_surrogate_pair_test_01_multi.js
diff --git a/test/codegen/expect/corelib/throw_half_surrogate_pair_test_01_multi.js b/test/codegen/expect/corelib/throw_half_surrogate_pair_test_01_multi.js
new file mode 100644
index 0000000000000000000000000000000000000000..f2dd163acb00a13ab7c03c9882857092503e3c8f
--- /dev/null
+++ b/test/codegen/expect/corelib/throw_half_surrogate_pair_test_01_multi.js
@@ -0,0 +1,18 @@
+dart_library.library('corelib/throw_half_surrogate_pair_test_01_multi', null, /* Imports */[
+  'dart_sdk'
+], function load__throw_half_surrogate_pair_test_01_multi(exports, dart_sdk) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const throw_half_surrogate_pair_test_01_multi = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  throw_half_surrogate_pair_test_01_multi.main = function() {
+    let trebleClef = "𝄞";
+    if (trebleClef[dartx.length] != 2) dart.throw("String should be a surrogate pair");
+    dart.throw(trebleClef[dartx.get](0));
+  };
+  dart.fn(throw_half_surrogate_pair_test_01_multi.main, VoidTodynamic());
+  // Exports:
+  exports.throw_half_surrogate_pair_test_01_multi = throw_half_surrogate_pair_test_01_multi;
+});