v8: back-port 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

Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
PR-URL: nodejs/node-v0.x-archive#25588

deps/v8/src/log.cc

@@ -1485,7 +1485,11 @@ void Logger::LogCodeObject(Object* object) {
         tag = Logger::STUB_TAG;
         break;
       case Code::BUILTIN:
-        description = "A builtin from the snapshot";
+        description =
+            Isolate::Current()->builtins()->Lookup(code_object->entry());
+        if (description == NULL) {
+          description = "A builtin from the snapshot";
+        }
         tag = Logger::BUILTIN_TAG;
         break;
       case Code::KEYED_LOAD_IC: