v8: cherry-pick JitCodeEvent patch from upstream

Original commit log follows:

    Meaningful name for builtins in JitCodeEvent API.

    Report builtins by name (e.g. "Builtin:ArgumentsAdaptorTrampoline")
    instead of labeling everything "Builtin:A builtin from the snapshot"

    Review URL: https://codereview.chromium.org/1216833002

PR-URL: https://github.com/nodejs/io.js/pull/2075
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

deps/v8/src/log.cc

@@ -1648,7 +1648,7 @@ void Logger::LogCodeObject(Object* object) {
       tag = Logger::REG_EXP_TAG;
       break;
     case Code::BUILTIN:
-      description = "A builtin from the snapshot";
+      description = isolate_->builtins()->name(code_object->builtin_index());
       tag = Logger::BUILTIN_TAG;
       break;
     case Code::HANDLER: