Heap::AllocateStringFromOneByte() and major part of its callers handlified.

src/scanner.cc

Index: src/scanner.cc
diff --git a/src/scanner.cc b/src/scanner.cc
index 67211e02921988e5846b5943184fef6419a7f105..fe75010c6ade94522250be38741ece8de3c19bc3 100644
--- a/src/scanner.cc
+++ b/src/scanner.cc
@@ -1118,13 +1118,19 @@ bool Scanner::ScanRegExpFlags() {
 
 Handle<String> Scanner::AllocateNextLiteralString(Isolate* isolate,
                                                   PretenureFlag tenured) {
+  MaybeHandle<String> maybe_result;
   if (is_next_literal_one_byte()) {
-    return isolate->factory()->NewStringFromOneByte(
-        Vector<const uint8_t>::cast(next_literal_one_byte_string()), tenured);
+    maybe_result = isolate->factory()->NewStringFromOneByte(
+        next_literal_one_byte_string(), tenured);
   } else {
-    return isolate->factory()->NewStringFromTwoByte(
-          next_literal_two_byte_string(), tenured);
+    maybe_result = isolate->factory()->NewStringFromTwoByte(
+        next_literal_two_byte_string(), tenured);
   }
+  // TODO(ishell): Temporarily returning null handle from here. I will proceed
+  // with maybehandlification in next CLs.
+  Handle<String> result;
+  if (!maybe_result.ToHandle(&result)) return Handle<String>();
+  return result;
 }