Move Object.assign implementation to C++

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 1060 matching lines @@
   Factory* factory = isolate->factory();
 
   Handle<ScriptContextTable> script_context_table =
       factory->NewScriptContextTable();
   native_context()->set_script_context_table(*script_context_table);
   InstallGlobalThisBinding();
 
   Handle<String> object_name = factory->Object_string();
   JSObject::AddProperty(
       global_object, object_name, isolate->object_function(), DONT_ENUM);
+  SimpleInstallFunction(isolate->object_function(),
+                        isolate->factory()->InternalizeUtf8String("assign"),
+                        Builtins::kObjectAssign, 2, false);
 
   Handle<JSObject> global(native_context()->global_object());
 
 
   {  // Install global Function object
     Handle<JSFunction> function_function =
         InstallFunction(global, "Function", JS_FUNCTION_TYPE, JSFunction::kSize,
                         empty_function, Builtins::kIllegal);
     function_function->initial_map()->set_is_callable();
     function_function->initial_map()->set_is_constructor(true);
@@ skipping 2203 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8