Make various string_util functions take StringPieces instead of char[].

components/autofill/core/browser/autofill_field.cc

Index: components/autofill/core/browser/autofill_field.cc
diff --git a/components/autofill/core/browser/autofill_field.cc b/components/autofill/core/browser/autofill_field.cc
index ffd6145033f3f3fbcad30e91bfd244fb00932fb0..183398181ecf5cad9741ef7d8fc09bb5b67710d0 100644
--- a/components/autofill/core/browser/autofill_field.cc
+++ b/components/autofill/core/browser/autofill_field.cc
@@ -291,12 +291,9 @@ void FillStreetAddress(const base::string16& value,
     return;
   }
 
-  base::string16 one_line_value;
-  const base::char16 kNewline[] = { '\n', 0 };
-  const base::string16 separator =
+  const base::string16& separator =
       l10n_util::GetStringUTF16(IDS_AUTOFILL_ADDRESS_LINE_SEPARATOR);
-  base::ReplaceChars(value, kNewline, separator, &one_line_value);
-  field->value = one_line_value;
+  base::ReplaceChars(value, base::ASCIIToUTF16("\n"), separator, &field->value);
 }
 
 std::string Hash32Bit(const std::string& str) {