Adopt absl::string_view in system_wrappers/

Bug: webrtc:13579
Change-Id: Id0e6515c63a3c9aa6d7effef7a2bd8b5ef35af09
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/262245
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Ali Tofigh <alito@webrtc.org>
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Xavier Lepaul‎ <xalep@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36904}
diff --git a/system_wrappers/source/field_trial.cc b/system_wrappers/source/field_trial.cc
index 1eac3dd..db49f63 100644
--- a/system_wrappers/source/field_trial.cc
+++ b/system_wrappers/source/field_trial.cc
@@ -69,7 +69,7 @@
 }
 }  // namespace
 
-bool FieldTrialsStringIsValid(const char* trials_string) {
+bool FieldTrialsStringIsValid(absl::string_view trials_string) {
   return FieldTrialsStringIsValidInternal(trials_string);
 }
 
@@ -88,7 +88,8 @@
   }
 }
 
-std::string MergeFieldTrialsStrings(const char* first, const char* second) {
+std::string MergeFieldTrialsStrings(absl::string_view first,
+                                    absl::string_view second) {
   std::map<std::string, std::string> fieldtrial_map;
   InsertOrReplaceFieldTrialStringsInMap(&fieldtrial_map, first);
   InsertOrReplaceFieldTrialStringsInMap(&fieldtrial_map, second);