[cronet] Expose API to set experimental options

components/cronet/ios/Cronet.mm

Index: components/cronet/ios/Cronet.mm
diff --git a/components/cronet/ios/Cronet.mm b/components/cronet/ios/Cronet.mm
index 135398acfe05aec622220113c65cd2e01d1d6134..d5384fdb1dd88d020b42a53a4fa4bc096718c851 100644
--- a/components/cronet/ios/Cronet.mm
+++ b/components/cronet/ios/Cronet.mm
@@ -36,6 +36,7 @@ BOOL gQuicEnabled = NO;
 cronet::URLRequestContextConfig::HttpCacheType gHttpCache =
     cronet::URLRequestContextConfig::HttpCacheType::DISK;
 ScopedVector<cronet::URLRequestContextConfig::QuicHint> gQuicHints;
+NSString* gExperimentalOptions = @"{}";
 NSString* gUserAgent = nil;
 BOOL gUserAgentPartial = NO;
 NSString* gSslKeyLogFileName = nil;
@@ -152,6 +153,11 @@ class CronetHttpProtocolHandlerDelegate
       base::SysNSStringToUTF8(host), port, altPort));
 }
 
++ (void)setExperimentalOptions:(NSString*)experimentalOptions {
+  [self checkNotStarted];
+  gExperimentalOptions = experimentalOptions;
+}
+
 + (void)setUserAgent:(NSString*)userAgent partial:(BOOL)partial {
   [self checkNotStarted];
   gUserAgent = userAgent;
@@ -197,6 +203,8 @@ class CronetHttpProtocolHandlerDelegate
 
   gChromeNet.Get()->set_http2_enabled(gHttp2Enabled);
   gChromeNet.Get()->set_quic_enabled(gQuicEnabled);
+  gChromeNet.Get()->set_experimental_options(
+      base::SysNSStringToUTF8(gExperimentalOptions));
   gChromeNet.Get()->set_http_cache(gHttpCache);
   gChromeNet.Get()->set_ssl_key_log_file_name(
       base::SysNSStringToUTF8(gSslKeyLogFileName));