Return MaybeHandle from NewExternalStringFrom*.

src/api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5452 matching lines @@
                                                                   right_string);
   // We do not expect this to fail. Change this if it does.
   CHECK(!result.is_null());
   return Utils::ToLocal(result);
 }
 
 
 static i::Handle<i::String> NewExternalStringHandle(
     i::Isolate* isolate,
     v8::String::ExternalStringResource* resource) {
-  i::Handle<i::String> result =
-      isolate->factory()->NewExternalStringFromTwoByte(resource);
   // We do not expect this to fail. Change this if it does.
-  CHECK(!result.is_null());
-  return result;
+  return isolate->factory()->NewExternalStringFromTwoByte(
+      resource).ToHandleChecked();
 }
 
 
 static i::Handle<i::String> NewExternalAsciiStringHandle(
     i::Isolate* isolate,
     v8::String::ExternalAsciiStringResource* resource) {
-  i::Handle<i::String> result =
-      isolate->factory()->NewExternalStringFromAscii(resource);
   // We do not expect this to fail. Change this if it does.
-  CHECK(!result.is_null());
-  return result;
+  return isolate->factory()->NewExternalStringFromAscii(
+      resource).ToHandleChecked();
 }
 
 
 Local<String> v8::String::NewExternal(
     Isolate* isolate,
     v8::String::ExternalStringResource* resource) {
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   EnsureInitializedForIsolate(i_isolate, "v8::String::NewExternal()");
   LOG_API(i_isolate, "String::NewExternal");
   ENTER_V8(i_isolate);
@@ skipping 2166 matching lines @@
   Isolate* isolate = reinterpret_cast<Isolate*>(info.GetIsolate());
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 } }  // namespace v8::internal