migrate to non-deprecated v8 functions

https://bugs.chromium.org/p/v8/issues/detail?id=8238

https://bugs.chromium.org/p/v8/issues/detail?id=7295

https://chromium-review.googlesource.com/c/v8/v8/+/1352273

native_mate/native_mate/dictionary.h

@@ -106,7 +106,9 @@ class Dictionary {
   bool SetMethod(const base::StringPiece& key, const T& callback) {
     return GetHandle()->Set(
         StringToV8(isolate_, key),
-        CallbackTraits<T>::CreateTemplate(isolate_, callback)->GetFunction());
+        CallbackTraits<T>::CreateTemplate(isolate_, callback)
+            ->GetFunction(isolate_->GetCurrentContext())
+            .ToLocalChecked());
   }
 
   bool Delete(const base::StringPiece& key) {

native_mate/native_mate/wrappable.cc

@@ -39,7 +39,8 @@ void WrappableBase::InitWith(v8::Isolate* isolate,
   // Call object._init if we have one.
   v8::Local<v8::Function> init;
   if (Dictionary(isolate, wrapper).Get("_init", &init))
-    init->Call(wrapper, 0, nullptr);
+    init->Call(isolate->GetCurrentContext(), wrapper, 0, nullptr)
+        .ToLocalChecked();
 
   AfterInit(isolate);
 }