Speed up common ObjectProtoToString cases

src/bootstrapper.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/bootstrapper.h"
 
 #include "src/accessors.h"
 #include "src/api-natives.h"
 #include "src/code-stubs.h"
 #include "src/extensions/externalize-string-extension.h"
@@ skipping 1569 matching lines @@
   Handle<FixedArray> embedder_data = factory->NewFixedArray(3);
   native_context()->set_embedder_data(*embedder_data);
 
   if (context_type == THIN_CONTEXT) return;
 
   {  // -- J S O N
     Handle<String> name = factory->InternalizeUtf8String("JSON");
     Handle<JSFunction> cons = factory->NewFunction(name);
     JSFunction::SetInstancePrototype(cons,
         Handle<Object>(native_context()->initial_object_prototype(), isolate));
-    cons->shared()->set_instance_class_name(*name);

[adamk, 2016/05/18 16:07:58]

This in the below are just cleanup because JSON and Math aren't constructible,
correct?

[Toon Verwaest, 2016/05/18 17:17:20]

It actually affects Object.prototype.toString.call(JSON) after deleting
toStringTag. I can either add a test and update the description, or move it out
of the CL...

[adamk, 2016/05/18 17:46:05]

Let's move it out of this CL, leaving it as a pure perf win, and do it in a
followup along with a test case.

     Handle<JSObject> json_object = factory->NewJSObject(cons, TENURED);
     DCHECK(json_object->IsJSObject());
     JSObject::AddProperty(global, name, json_object, DONT_ENUM);
   }
 
   {  // -- M a t h
     Handle<String> name = factory->InternalizeUtf8String("Math");
     Handle<JSFunction> cons = factory->NewFunction(name);
     JSFunction::SetInstancePrototype(
         cons,
         Handle<Object>(native_context()->initial_object_prototype(), isolate));
-    cons->shared()->set_instance_class_name(*name);
     Handle<JSObject> math = factory->NewJSObject(cons, TENURED);
     DCHECK(math->IsJSObject());
     JSObject::AddProperty(global, name, math, DONT_ENUM);
     SimpleInstallFunction(math, "acos", Builtins::kMathAcos, 1, true);
     SimpleInstallFunction(math, "asin", Builtins::kMathAsin, 1, true);
     SimpleInstallFunction(math, "atan", Builtins::kMathAtan, 1, true);
     SimpleInstallFunction(math, "ceil", Builtins::kMathCeil, 1, true);
     SimpleInstallFunction(math, "clz32", Builtins::kMathClz32, 1, true);
     Handle<JSFunction> math_floor =
         SimpleInstallFunction(math, "floor", Builtins::kMathFloor, 1, true);
@@ skipping 2161 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8