[runtime] Introduce dedicated JSBoundFunction to represent bound functions.

src/api.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.
 
 #include "src/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 4504 matching lines @@
   if (!func->shared()->script()->IsScript()) {
     return v8::UnboundScript::kNoScriptId;
   }
   i::Handle<i::Script> script(i::Script::cast(func->shared()->script()));
   return script->id();
 }
 
 
 Local<v8::Value> Function::GetBoundFunction() const {
   auto self = Utils::OpenHandle(this);
-  if (!self->IsJSFunction()) {
-    return v8::Undefined(reinterpret_cast<v8::Isolate*>(self->GetIsolate()));
+  if (self->IsJSBoundFunction()) {
+    auto bound_function = i::Handle<i::JSBoundFunction>::cast(self);
+    auto bound_target_function = i::handle(
+        bound_function->bound_target_function(), bound_function->GetIsolate());
+    return Utils::CallableToLocal(bound_target_function);
   }
-  auto func = i::Handle<i::JSFunction>::cast(self);
-  if (!func->shared()->bound()) {
-    return v8::Undefined(reinterpret_cast<v8::Isolate*>(func->GetIsolate()));
-  }
-  i::Handle<i::BindingsArray> bound_args = i::Handle<i::BindingsArray>(
-      i::BindingsArray::cast(func->function_bindings()));
-  i::Handle<i::Object> original(bound_args->bound_function(),
-                                func->GetIsolate());
-  return Utils::CallableToLocal(i::Handle<i::JSFunction>::cast(original));
+  return v8::Undefined(reinterpret_cast<v8::Isolate*>(self->GetIsolate()));
 }
 
 
 int Name::GetIdentityHash() {
   auto self = Utils::OpenHandle(this);
   return static_cast<int>(self->Hash());
 }
 
 
 int String::Length() const {
@@ skipping 3945 matching lines @@
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 }  // namespace internal
 }  // namespace v8