pkg/vm_service_client: add getSourceReport to VMServiceReference

test/client_test.dart

Index: test/client_test.dart
diff --git a/test/client_test.dart b/test/client_test.dart
index f7e7cba0863f256d9b25b5d56da2d7acc01273de..ca7b2b18fc33053468f1e6ee0cdb90281ead4f51 100644
--- a/test/client_test.dart
+++ b/test/client_test.dart
@@ -21,7 +21,7 @@ void main() {
     client = await runAndConnect();
     var version = await client.getVersion();
     expect(version.major, equals(3));
-    expect(version.minor, new isInstanceOf<int>());
+    expect(version.minor, greaterThanOrEqualTo(4));
   });
 
   test("considers the VM service version valid", () async {