Adopt absl::string_view in rtc_base/string_encode.*

Bug: webrtc:13579
Change-Id: If52108d151a12bde0e8d552ce7940948c08cef3a
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/256812
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Jakob Ivarsson‎ <jakobi@webrtc.org>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Commit-Queue: Ali Tofigh <alito@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36424}
diff --git a/rtc_base/buffer_unittest.cc b/rtc_base/buffer_unittest.cc
index 8beae43..b56118a 100644
--- a/rtc_base/buffer_unittest.cc
+++ b/rtc_base/buffer_unittest.cc
@@ -13,6 +13,7 @@
 #include <cstdint>
 #include <utility>
 
+#include "absl/strings/string_view.h"
 #include "api/array_view.h"
 #include "test/gmock.h"
 #include "test/gtest.h"
@@ -73,6 +74,13 @@
   EXPECT_EQ(0, memcmp(buf.data(), kTestData, 16));
 }
 
+TEST(BufferTest, TestStringViewConversion) {
+  Buffer buf(kTestData);
+  absl::string_view view = buf;
+  EXPECT_EQ(view,
+            absl::string_view(reinterpret_cast<const char*>(kTestData), 16u));
+}
+
 TEST(BufferTest, TestSetData) {
   Buffer buf(kTestData + 4, 7);
   buf.SetData(kTestData, 9);