Add a complex reload test that rebases the root script path three times.

runtime/observatory/lib/src/service/object.dart

Index: runtime/observatory/lib/src/service/object.dart
diff --git a/runtime/observatory/lib/src/service/object.dart b/runtime/observatory/lib/src/service/object.dart
index e0f6e055920eee8fa6b9a594f19a7a0e95bfa2ca..c638dd90d9f4a0bf88b162f28d10e2337f86bc70 100644
--- a/runtime/observatory/lib/src/service/object.dart
+++ b/runtime/observatory/lib/src/service/object.dart
@@ -1333,9 +1333,19 @@ class Isolate extends ServiceObjectOwner implements M.Isolate {
     return invokeRpc('getSourceReport', params);
   }
 
-  Future<ServiceMap> reloadSources() {
-    return invokeRpc('_reloadSources', {}).then((_) {
+  Future<ServiceMap> reloadSources(
+      {String rootLibUri,
+       bool pause}) {
+    Map<String, dynamic> params = <String, dynamic>{};
+    if (rootLibUri != null) {
+      params['rootLibUri'] = rootLibUri;
+    }
+    if (pause != null) {
+      params['pause'] = pause;
+    }
+    return invokeRpc('reloadSources', params).then((result) {
       reloading = true;
+      return result;
     });
   }