[runtime] Add %ToString and %_ToString and remove the TO_STRING builtin.

src/x64/interface-descriptors-x64.cc

 // Copyright 2012 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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/interface-descriptors.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 89 matching lines @@
 
 void ToNumberDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   // ToNumberStub invokes a function, and therefore needs a context.
   Register registers[] = {rax};
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
 
 
 // static
+const Register ToStringDescriptor::ReceiverRegister() { return rax; }
+
+
+// static
 const Register ToObjectDescriptor::ReceiverRegister() { return rax; }
 
 
 void NumberToStringDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {rax};
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
 
 
@@ skipping 245 matching lines @@
       rdi,  // math rounding function
       rdx,  // vector slot id
       rbx   // type vector
   };
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64