Return MaybeHandle from NewRaw???String.

test/cctest/test-mementos.cc

 // Copyright 2014 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
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@@ skipping 21 matching lines @@
 
 static void SetUpNewSpaceWithPoisonedMementoAtTop() {
   Isolate* isolate = CcTest::i_isolate();
   Heap* heap = isolate->heap();
   NewSpace* new_space = heap->new_space();
 
   // Make sure we can allocate some objects without causing a GC later.
   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
   // site pointer.
   AllocationMemento* memento =
       reinterpret_cast<AllocationMemento*>(new_space->top() + kHeapObjectTag);
   memento->set_map_no_write_barrier(heap->allocation_memento_map());
   memento->set_allocation_site(
       reinterpret_cast<AllocationSite*>(kHeapObjectTag), SKIP_WRITE_BARRIER);
 }
@@ skipping 61 matching lines @@
   AllocationMemento* memento =
       reinterpret_cast<AllocationMemento*>(memento_address + kHeapObjectTag);
   CHECK_EQ(memento->map(), heap->allocation_memento_map());
 
   // Furthermore, how many mementos did we create? The count should match
   // call_count - SharedFunctionInfo::kGenerousAllocationCount.
   AllocationSite* site = memento->GetAllocationSite();
   CHECK_EQ(call_count - SharedFunctionInfo::kGenerousAllocationCount,
            site->pretenure_create_count()->value());
 }