[Cronet] Integrate CrNet functionality into Cronet on iOS.

components/cronet/ios/Cronet+TestSupport.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 "components/cronet/ios/Cronet.h"
+
+// Cronet test support category.
+@interface Cronet (TestSupport)
+
+// Sets Host Resolver Rules for testing.
+// This method only has any effect before |start| is called.
++ (void)setHostResolverRulesForTesting:(NSString*)hostResolverRulesForTesting;
+
+// Sets a native MockCertVerifier for testing.
+// This method only has any effect before |start| is called.
++ (void)setMockCertVerifierForTesting:(void*)mockCertVerifierForTesting;
+
+@end