deps: cherry-pick r21297 from v8 trunk

Changes the return value of PropertyCallbackInfo<T>::This() from
Local<Value> back to Local<Object>.  See [1] and [2] for background.

[1] https://groups.google.com/forum/#!topic/v8-users/wP2UcQ4cBW4
[2] https://codereview.chromium.org/285643008/

Signed-off-by: Fedor Indutny <fedor@indutny.com>

deps/v8/include/v8.h

@@ -2493,7 +2493,7 @@ class PropertyCallbackInfo {
  public:
   V8_INLINE Isolate* GetIsolate() const;
   V8_INLINE Local<Value> Data() const;
-  V8_INLINE Local<Value> This() const;
+  V8_INLINE Local<Object> This() const;
   V8_INLINE Local<Object> Holder() const;
   V8_INLINE ReturnValue<T> GetReturnValue() const;
   // This shouldn't be public, but the arm compiler needs it.
@@ -6488,8 +6488,8 @@ Local<Value> PropertyCallbackInfo<T>::Data() const {
 
 
 template<typename T>
-Local<Value> PropertyCallbackInfo<T>::This() const {
-  return Local<Value>(reinterpret_cast<Value*>(&args_[kThisIndex]));
+Local<Object> PropertyCallbackInfo<T>::This() const {
+  return Local<Object>(reinterpret_cast<Object*>(&args_[kThisIndex]));
 }
 
 

deps/v8/src/accessors.cc

@@ -20,6 +20,16 @@ namespace v8 {
 namespace internal {
 
 
+// We have a slight impedance mismatch between the external API and the way we
+// use callbacks internally: Externally, callbacks can only be used with
+// v8::Object, but internally we even have callbacks on entities which are
+// higher in the hierarchy, so we can only return i::Object here, not
+// i::JSObject.
+Handle<Object> GetThisFrom(const v8::PropertyCallbackInfo<v8::Value>& info) {
+  return Utils::OpenHandle(*v8::Local<v8::Value>(info.This()));
+}
+
+
 Handle<AccessorInfo> Accessors::MakeAccessor(
     Isolate* isolate,
     Handle<String> name,
@@ -146,7 +156,7 @@ void Accessors::ArrayLengthGetter(
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(info.GetIsolate());
   DisallowHeapAllocation no_allocation;
   HandleScope scope(isolate);
-  Object* object = *Utils::OpenHandle(*info.This());
+  Object* object = *GetThisFrom(info);
   // Traverse the prototype chain until we reach an array.
   JSArray* holder = FindInstanceOf<JSArray>(isolate, object);
   Object* result;
@@ -229,7 +239,7 @@ void Accessors::StringLengthGetter(
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(info.GetIsolate());
   DisallowHeapAllocation no_allocation;
   HandleScope scope(isolate);
-  Object* value = *Utils::OpenHandle(*info.This());
+  Object* value = *GetThisFrom(info);
   Object* result;
   if (value->IsJSValue()) value = JSValue::cast(value)->value();
   if (value->IsString()) {
@@ -824,7 +834,7 @@ void Accessors::FunctionPrototypeGetter(
     const v8::PropertyCallbackInfo<v8::Value>& info) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(info.GetIsolate());
   HandleScope scope(isolate);
-  Handle<Object> object = Utils::OpenHandle(*info.This());
+  Handle<Object> object = GetThisFrom(info);
   Handle<Object> result = GetFunctionPrototype(isolate, object);
   info.GetReturnValue().Set(Utils::ToLocal(result));
 }
@@ -864,7 +874,7 @@ void Accessors::FunctionLengthGetter(
     const v8::PropertyCallbackInfo<v8::Value>& info) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(info.GetIsolate());
   HandleScope scope(isolate);
-  Handle<Object> object = Utils::OpenHandle(*info.This());
+  Handle<Object> object = GetThisFrom(info);
   MaybeHandle<JSFunction> maybe_function;
 
   {
@@ -922,7 +932,7 @@ void Accessors::FunctionNameGetter(
     const v8::PropertyCallbackInfo<v8::Value>& info) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(info.GetIsolate());
   HandleScope scope(isolate);
-  Handle<Object> object = Utils::OpenHandle(*info.This());
+  Handle<Object> object = GetThisFrom(info);
   MaybeHandle<JSFunction> maybe_function;
 
   {
@@ -1071,7 +1081,7 @@ void Accessors::FunctionArgumentsGetter(
     const v8::PropertyCallbackInfo<v8::Value>& info) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(info.GetIsolate());
   HandleScope scope(isolate);
-  Handle<Object> object = Utils::OpenHandle(*info.This());
+  Handle<Object> object = GetThisFrom(info);
   MaybeHandle<JSFunction> maybe_function;
 
   {
@@ -1210,7 +1220,7 @@ void Accessors::FunctionCallerGetter(
     const v8::PropertyCallbackInfo<v8::Value>& info) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(info.GetIsolate());
   HandleScope scope(isolate);
-  Handle<Object> object = Utils::OpenHandle(*info.This());
+  Handle<Object> object = GetThisFrom(info);
   MaybeHandle<JSFunction> maybe_function;
   {
     DisallowHeapAllocation no_allocation;