Fix a variety of service protocol bugs.

runtime/vm/json_test.cc

Index: runtime/vm/json_test.cc
diff --git a/runtime/vm/json_test.cc b/runtime/vm/json_test.cc
index 5bce0d396f9db8d8ad4635f688f0cf00d0b60ea3..6ca6760fba38b2ecbfc28b0c11ae060205d9a3ba 100644
--- a/runtime/vm/json_test.cc
+++ b/runtime/vm/json_test.cc
@@ -299,8 +299,12 @@ TEST_CASE(JSON_JSONStream_DartObject) {
     JSONObject jsobj(&jsarr);
     jsobj.AddProperty("object_key", Object::Handle(Object::null()));
   }
+  char buffer[1024];
+  ElideJSONSubstring("classes", js.ToCString(), buffer);
   EXPECT_STREQ("[{\"type\":\"@Instance\","
                "\"_vmType\":\"null\","
+               "\"class\":{\"type\":\"@Class\",\"fixedId\":true,\"id\":\"\","
+               "\"name\":\"Null\"},"
                "\"kind\":\"Null\","
                "\"fixedId\":true,"
                "\"id\":\"objects\\/null\","
@@ -308,11 +312,13 @@ TEST_CASE(JSON_JSONStream_DartObject) {
                "{\"object_key\":"
                "{\"type\":\"@Instance\","
                "\"_vmType\":\"null\","
+               "\"class\":{\"type\":\"@Class\",\"fixedId\":true,\"id\":\"\","
+               "\"name\":\"Null\"},"
                "\"kind\":\"Null\","
                "\"fixedId\":true,"
                "\"id\":\"objects\\/null\","
                "\"valueAsString\":\"null\"}}]",
-               js.ToCString());
+               buffer);
 }
 
 TEST_CASE(JSON_JSONStream_EscapedString) {