Adopt absl::string_view in function parameters under rtc_base/

This is part of a large-scale effort to increase adoption of
absl::string_view across the WebRTC code base.

This CL converts the majority of "const std::string&"s in function
parameters under rtc_base/ to absl::string_view.

Bug: webrtc:13579
Change-Id: I2b1e3776aa42326aa405f76bb324a2d233b21dca
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/254081
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Xavier Lepaul‎ <xalep@webrtc.org>
Reviewed-by: Anders Lilienthal <andersc@webrtc.org>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Commit-Queue: Ali Tofigh <alito@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36239}
diff --git a/rtc_base/openssl_key_pair.h b/rtc_base/openssl_key_pair.h
index d9a4939..d09bdb0 100644
--- a/rtc_base/openssl_key_pair.h
+++ b/rtc_base/openssl_key_pair.h
@@ -16,6 +16,7 @@
 #include <memory>
 #include <string>
 
+#include "absl/strings/string_view.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/ssl_identity.h"
 
@@ -34,7 +35,7 @@
   // Constructs a key pair from the private key PEM string. This must not result
   // in missing public key parameters. Returns null on error.
   static std::unique_ptr<OpenSSLKeyPair> FromPrivateKeyPEMString(
-      const std::string& pem_string);
+      absl::string_view pem_string);
 
   ~OpenSSLKeyPair();