Fix internal NSM helper to use a Dart Symbol

Not sure if this entirely handles #470, but it does fix the breaking example.

[email protected]

Review URL: https://codereview.chromium.org/1754773002 .

Author: vsmenon

pkg/dev_compiler/lib/runtime/dart/_runtime.js

@@ -426,8 +426,11 @@ dart_library.library('dart/_runtime', null, /* Imports */[
     }
     return true;
   }
+  function _dartSymbol(name) {
+    return const_(core.Symbol.new(name.toString()));
+  }
   function throwNoSuchMethod(obj, name, pArgs, nArgs, extras) {
-    throw_(new core.NoSuchMethodError(obj, name, pArgs, nArgs, extras));
+    throw_(new core.NoSuchMethodError(obj, _dartSymbol(name), pArgs, nArgs, extras));
   }
   function throwNoSuchMethodFunc(obj, name, pArgs, opt_func) {
     if (obj === void 0) obj = opt_func;

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/operations.dart

@@ -74,9 +74,12 @@ checkApply(type, actuals) => JS('', '''(() => {
   return true;
 })()''');
 
+_dartSymbol(name) => JS('', '''
+  $const_($Symbol.new($name.toString()))
+''');
 
 throwNoSuchMethod(obj, name, pArgs, nArgs, extras) => JS('', '''(() => {
-  $throw_(new $NoSuchMethodError($obj, $name, $pArgs, $nArgs, $extras));
+  $throw_(new $NoSuchMethodError($obj, $_dartSymbol($name), $pArgs, $nArgs, $extras));
 })()''');
 
 throwNoSuchMethodFunc(obj, name, pArgs, opt_func) => JS('', '''(() => {