Use FieldTrialsView::IsEnabled for DTLS 1.3

No behavior changes.

Bug: webrtc:383141571, chromium:433885045
Change-Id: Ice5f3e5cbd245ddea407248a6f29c61c646e6a72
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/401740
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Guido Urdaneta <guidou@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#45206}
diff --git a/rtc_base/openssl_stream_adapter.cc b/rtc_base/openssl_stream_adapter.cc
index 7d7466b..604a946 100644
--- a/rtc_base/openssl_stream_adapter.cc
+++ b/rtc_base/openssl_stream_adapter.cc
@@ -144,13 +144,15 @@
     return kForceDtls13Off;
   }
 #ifdef DTLS1_3_VERSION
-  auto mode = field_trials->Lookup("WebRTC-ForceDtls13");
-  RTC_LOG(LS_WARNING) << "WebRTC-ForceDtls13: " << mode;
-  if (mode == "Enabled") {
+  if (field_trials->IsEnabled("WebRTC-ForceDtls13")) {
+    RTC_LOG(LS_WARNING) << "WebRTC-ForceDtls13 Enabled";
     return kForceDtls13Enabled;
-  } else if (mode == "Only") {
+  }
+  if (field_trials->Lookup("WebRTC-ForceDtls13") == "Only") {
+    RTC_LOG(LS_WARNING) << "WebRTC-ForceDtls13 Only";
     return kForceDtls13Only;
   }
+  RTC_LOG(LS_WARNING) << "WebRTC-ForceDtls13 Disabled";
 #endif
   return kForceDtls13Off;
 }