Return MaybeHandle from NewRaw???String.

test/cctest/test-mementos.cc

Index: test/cctest/test-mementos.cc
diff --git a/test/cctest/test-mementos.cc b/test/cctest/test-mementos.cc
index 1dc38f9af5cef8d59af377f2a255f9577b95880f..a377b4a4c6f31c0a8139f3dc9d1ae95ee37de817 100644
--- a/test/cctest/test-mementos.cc
+++ b/test/cctest/test-mementos.cc
@@ -39,7 +39,8 @@ static void SetUpNewSpaceWithPoisonedMementoAtTop() {
   heap->CollectAllGarbage(Heap::kAbortIncrementalMarkingMask);
 
   // Allocate a string, the GC may suspect a memento behind the string.
-  Handle<SeqOneByteString> string = isolate->factory()->NewRawOneByteString(12);
+  Handle<SeqOneByteString> string =
+      isolate->factory()->NewRawOneByteString(12).ToHandleChecked();
   CHECK(*string);
 
   // Create an allocation memento behind the string with a garbage allocation