Revert of Moving gRPC support interfaces out of cronet and into a new component.

components/cronet/ios/test/start_cronet.mm

-// 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 <Cronet/Cronet.h>
-#import <Foundation/Foundation.h>
-
-#include "components/cronet/ios/test/start_cronet.h"
-
-#include "base/at_exit.h"
-#include "components/grpc_support/test/quic_test_server.h"
-
-namespace cronet {
-
-base::AtExitManager* g_at_exit_ = nullptr;
-
-void StartCronetIfNecessary() {
-  static bool initialized = false;
-  if (!initialized) {
-    initialized = true;
-    [Cronet setUserAgent:@"CronetTest/1.0.0.0" partial:NO];
-    [Cronet setHttp2Enabled:true];
-    [Cronet setQuicEnabled:true];
-    [Cronet setSslKeyLogFileName:@"SSLKEYLOGFILE"];
-    [Cronet addQuicHint:@"test.example.com"
-                   port:grpc_support::kTestServerPort
-                altPort:grpc_support::kTestServerPort];
-    [Cronet enableTestCertVerifierForTesting];
-    [Cronet
-        setHostResolverRulesForTesting:@"MAP test.example.com 127.0.0.1,"
-                                        "MAP notfound.example.com ~NOTFOUND"];
-    [Cronet start];
-
-    // This method must be called once from the main thread.
-    if (!g_at_exit_)
-      g_at_exit_ = new base::AtExitManager;
-  }
-}
-
-}  // namespace cronet