Move symbol table from per isolate snapshot to vm isolate snapshot, this reduces the per isolate in…

runtime/vm/service_test.cc

Index: runtime/vm/service_test.cc
===================================================================
--- runtime/vm/service_test.cc	(revision 45789)
+++ runtime/vm/service_test.cc	(working copy)
@@ -35,8 +35,10 @@
     }
 
     // Parse the message.
-    SnapshotReader reader(message->data(), message->len(), Snapshot::kMessage,
-                          Isolate::Current(), Thread::Current()->zone());
+    MessageSnapshotReader reader(message->data(),
+                                 message->len(),
+                                 Isolate::Current(),
+                                 Thread::Current()->zone());
     const Object& response_obj = Object::Handle(reader.ReadObject());
     String& response = String::Handle();
     response ^= response_obj.raw();