Expose allocation tracing over service protocol

runtime/observatory/tests/service/test_helper.dart

Index: runtime/observatory/tests/service/test_helper.dart
diff --git a/runtime/observatory/tests/service/test_helper.dart b/runtime/observatory/tests/service/test_helper.dart
index f47f1cd45e9bfbf3778be5e9a793482a222146cf..122c9cd3f82cb1cc47e578d9fe60c2b21f92bac9 100644
--- a/runtime/observatory/tests/service/test_helper.dart
+++ b/runtime/observatory/tests/service/test_helper.dart
@@ -196,6 +196,18 @@ Future<Isolate> resumeIsolate(Isolate isolate) {
 }
 
 
+Future<Class> getClassFromRootLib(Isolate isolate, String className) async {
+  Library rootLib = await isolate.rootLibrary.load();
+  for (var i = 0; i < rootLib.classes.length; i++) {
+    Class cls = rootLib.classes[i];
+    if (cls.name == className) {
+      return cls;
+    }
+  }
+  return null;
+}
+
+
 /// Runs [tests] in sequence, each of which should take an [Isolate] and
 /// return a [Future]. Code for setting up state can run before and/or
 /// concurrently with the tests. Uses [mainArgs] to determine whether