fix test runner to understand mutlitests that expect an error

pkg/dev_compiler/tool/run.js

Index: pkg/dev_compiler/tool/run.js
diff --git a/pkg/dev_compiler/tool/run.js b/pkg/dev_compiler/tool/run.js
index a9c8c3e26c85ddd670e3fb5b9461c437943eabeb..71c4b896e924013dcbb3b2326cba187f4972c3ac 100644
--- a/pkg/dev_compiler/tool/run.js
+++ b/pkg/dev_compiler/tool/run.js
@@ -44,7 +44,15 @@ requirejs.config({
 var sdk = requirejs('dart_sdk');
 sdk.dart.ignoreWhitelistedErrors(false);
 
+let negative = /negative_test/.test(test);
 function finish(e) {
+  if (negative) {
+    if (e) {
+      e = null;
+    } else {
+      e = new Error("test marked as 'negative' but did not throw");
+    }
+  }
   if (e) {
     console.log('Test ' + test + ' failed:\n' + e.toString());
     sdk.dart.stackPrint(e);
@@ -66,6 +74,7 @@ async_helper.asyncTestInitialize(finish);
 var module = requirejs(test);
 var lib = test.split('/').slice(-1)[0];
 try {
+  if (module[lib]._expectRuntimeError) negative = true;
   var result = module[lib].main();
   // async_helper tests call finish directly - call here for all other
   // tests.