fix #470, string interpolation now respects Dart toString

test/codegen/expect/BenchmarkBase.js

Index: test/codegen/expect/BenchmarkBase.js
diff --git a/test/codegen/expect/BenchmarkBase.js b/test/codegen/expect/BenchmarkBase.js
index 8f200b5b8d8d75a844f5022385346afbc4912b64..69d57f97b2b2631a855a2376888f2bfa0fbd77a8 100644
--- a/test/codegen/expect/BenchmarkBase.js
+++ b/test/codegen/expect/BenchmarkBase.js
@@ -9,12 +9,12 @@ dart_library.library('BenchmarkBase', null, /* Imports */[
   BenchmarkBase$.Expect = class Expect extends core.Object {
     static equals(expected, actual) {
       if (!dart.equals(expected, actual)) {
-        dart.throw(`Values not equal: ${expected} vs ${actual}`);
+        dart.throw(dart.str`Values not equal: ${expected} vs ${actual}`);
       }
     }
     static listEquals(expected, actual) {
       if (expected[dartx.length] != actual[dartx.length]) {
-        dart.throw(`Lists have different lengths: ${expected[dartx.length]} vs ${actual[dartx.length]}`);
+        dart.throw(dart.str`Lists have different lengths: ${expected[dartx.length]} vs ${actual[dartx.length]}`);
       }
       for (let i = 0; i < dart.notNull(actual[dartx.length]); i++) {
         BenchmarkBase$.Expect.equals(expected[dartx.get](i), actual[dartx.get](i));
@@ -73,7 +73,7 @@ dart_library.library('BenchmarkBase', null, /* Imports */[
     }
     report() {
       let score = this.measure();
-      core.print(`${this.name}(RunTime): ${score} us.`);
+      core.print(dart.str`${this.name}(RunTime): ${score} us.`);
     }
   };
   dart.setSignature(BenchmarkBase$.BenchmarkBase, {