Fix language/stacktrace_rethrow_error_test_withtraceparameter_multi test

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

Index: pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/utils.dart
diff --git a/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/utils.dart b/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/utils.dart
index ac133fe2c0d101750b9da474768f5541c48e1dc2..05d871798cbb1d951365bec2585f97abf839b983 100644
--- a/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/utils.dart
+++ b/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/utils.dart
@@ -24,13 +24,13 @@ final hasOwnProperty = JS('', 'Object.prototype.hasOwnProperty');
 /// This error indicates a strong mode specific failure, other than a type
 /// assertion failure (TypeError) or CastError.
 void throwStrongModeError(String message) {

[Leaf, 2017/05/15 22:06:39]

The only word of dart in this method is `if`.  Maybe should just be a full JS
body?

-  if (_trapRuntimeErrors) JS('', 'debugger');
+  if (JS('bool', 'dart.__trapRuntimeErrors')) JS('', 'debugger');
   JS('', 'throw new #(#);', StrongModeErrorImplementation, message);
 }
 
 /// This error indicates a bug in the runtime or the compiler.
 void throwInternalError(String message) {
-  if (_trapRuntimeErrors) JS('', 'debugger');
+  if (JS('bool', 'dart.__trapRuntimeErrors')) JS('', 'debugger');
   JS('', 'throw Error(#)', message);

[Leaf, 2017/05/15 22:06:40]

likewise.

 }