Revert of [cronet] Expose API to set experimental options

components/cronet/ios/test/start_cronet.mm

Index: components/cronet/ios/test/start_cronet.mm
diff --git a/components/cronet/ios/test/start_cronet.mm b/components/cronet/ios/test/start_cronet.mm
index 00781cfdd375307b30f15190a5181402fcfdd068..148fe5333f2101a0e5afe1e14d3f768a5b479f54 100644
--- a/components/cronet/ios/test/start_cronet.mm
+++ b/components/cronet/ios/test/start_cronet.mm
@@ -21,7 +21,7 @@
     [Cronet setHttp2Enabled:true];
     [Cronet setQuicEnabled:true];
     [Cronet setAcceptLanguages:@"en-US,en"];
-    [Cronet setExperimentalOptions:@"{\"ssl_key_log_file\":\"SSLKEYLOGFILE\"}"];
+    [Cronet setSslKeyLogFileName:@"SSLKEYLOGFILE"];
     [Cronet addQuicHint:@"test.example.com" port:443 altPort:443];
     [Cronet enableTestCertVerifierForTesting];
     [Cronet start];