Use StringPiece more in base::Value interfaces.

components/domain_reliability/context_unittest.cc

Index: components/domain_reliability/context_unittest.cc
diff --git a/components/domain_reliability/context_unittest.cc b/components/domain_reliability/context_unittest.cc
index d68d9db4f3a0dc226c5818356ae897bcb12783c9..bdaf46337222164610363e75c9d47c82e7c798c6 100644
--- a/components/domain_reliability/context_unittest.cc
+++ b/components/domain_reliability/context_unittest.cc
@@ -13,6 +13,7 @@
 
 #include "base/bind.h"
 #include "base/json/json_reader.h"
+#include "base/strings/string_piece.h"
 #include "components/domain_reliability/beacon.h"
 #include "components/domain_reliability/dispatcher.h"
 #include "components/domain_reliability/scheduler.h"
@@ -60,8 +61,8 @@ std::unique_ptr<DomainReliabilityBeacon> MakeBeacon(MockableTime* time) {
 }
 
 template <typename ValueType,
-          bool (DictionaryValue::* GetValueType)(const std::string&,
-                                                 ValueType*) const>
+          bool (DictionaryValue::*GetValueType)(base::StringPiece, ValueType*)
+              const>
 struct HasValue {
   bool operator()(const DictionaryValue& dict,
                   const std::string& key,