[cronet] Expose API to set experimental options

components/cronet/ios/Cronet.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import <Foundation/Foundation.h>
 
 #include "bidirectional_stream_c.h"
 
 // TODO(mef): Remove this header after transition to bidirectional_stream_c.h
 // See crbug.com/650462 for details.
@@ skipping 30 matching lines @@
 
 // Set HTTP Cache type to be used by CronetEngine.  This method only has any
 // effect before |start| is called.  See HttpCacheType enum for available
 // options.
 + (void)setHttpCacheType:(CRNHttpCacheType)httpCacheType;
 
 // Adds hint that host supports QUIC on altPort. This method only has any effect
 // before |start| is called.
 + (void)addQuicHint:(NSString*)host port:(int)port altPort:(int)altPort;
 
+// Set experimental Cronet options.  Argument is a JSON string; see
+// |URLRequestContextConfig| for more details.  This method only has
+// any effect before |start| is called.
++ (void)setExperimentalOptions:(NSString*)experimentalOptions;
+
 // Sets the User-Agent request header string to be sent with all requests.
 // If |partial| is set to YES, then actual user agent value is based on device
 // model, OS version, and |userAgent| argument. For example "Foo/3.0.0.0" is
 // sent as "Mozilla/5.0 (iPhone; CPU iPhone OS 9_3 like Mac OS X)
 // AppleWebKit/601.1 (KHTML, like Gecko) Foo/3.0.0.0 Mobile/15G31
 // Safari/601.1.46".
 // If |partial| is set to NO, then |userAgent| value is complete value sent to
 // the remote. For Example: "Foo/3.0.0.0" is sent as "Foo/3.0.0.0".
 //
 // This method only has any effect before |start| is called.
@@ skipping 67 matching lines @@
 
 // Sets Host Resolver Rules for testing.
 // This method must be called after |start| has been called.
 + (void)setHostResolverRulesForTesting:(NSString*)hostResolverRulesForTesting;
 
 // Enables TestCertVerifier which accepts all certificates for testing.
 // This method only has any effect before |start| is called.
 + (void)enableTestCertVerifierForTesting;
 
 @end