Source positions for constructors and lots of async machinery

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 58de4e660f99ff402c5d1a2dd1bc5573690a900f..01704152c16bfe6876f5c001ef0023cf60956dce 100644
--- a/runtime/observatory/tests/service/test_helper.dart
+++ b/runtime/observatory/tests/service/test_helper.dart
@@ -255,9 +255,11 @@ IsolateTest stoppedAtLine(int line) {
 
     Frame top = frames[0];
     Script script = await top.location.script.load();
-    if (script.tokenToLine(top.location.tokenPos) != line) {
+    int actualLine = script.tokenToLine(top.location.tokenPos);
+    if (actualLine != line) {
       var sb = new StringBuffer();
-      sb.write("Expected to be at line $line, but got stack trace:\n");
+      sb.write("Expected to be at line $line but actually at line $actualLine");
+      sb.write("\nFull stack trace:\n");
       for (Frame f in stack['frames']) {
         sb.write(" $f\n");
       }