[cronet] Add mechanism for restarting CronetEnvironment

components/cronet/ios/test/cronet_http_test.mm

 // Copyright 2015 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 <stdint.h>
 
 #include "base/logging.h"
@@ skipping 122 matching lines @@
   HttpTest() {}
   ~HttpTest() override {}
 
   void SetUp() override {
     grpc_support::StartQuicTestServer();
     TestServer::Start();
 
     [Cronet setRequestFilterBlock:^(NSURLRequest* request) {
       return YES;
     }];
-    StartCronetIfNecessary(grpc_support::GetQuicTestServerPort());
+    StartCronet(grpc_support::GetQuicTestServerPort());
     [Cronet registerHttpProtocolHandler];
     NSURLSessionConfiguration* config =
         [NSURLSessionConfiguration ephemeralSessionConfiguration];
     [Cronet installIntoSessionConfiguration:config];
     delegate_.reset([[TestDelegate alloc] init]);
     NSURLSession* session = [NSURLSession sessionWithConfiguration:config
                                                           delegate:delegate_
                                                      delegateQueue:nil];
     // Take a reference to the session and store it so it doesn't get
     // deallocated until this object does.
     session_.reset([session retain]);
   }
 
   void TearDown() override {
     grpc_support::ShutdownQuicTestServer();
     TestServer::Shutdown();
+
+    [Cronet stopNetLog];
+    [Cronet shutdown];
   }
 
   // Launches the supplied |task| and blocks until it completes, with a timeout
   // of 1 second.
   void StartDataTaskAndWaitForCompletion(NSURLSessionDataTask* task) {
     [delegate_ reset];
     [task resume];
     int64_t deadline_ns = 20 * ns_in_second;
     ASSERT_EQ(0, dispatch_semaphore_wait(
                      [delegate_ semaphore],
@@ skipping 281 matching lines @@
   [Cronet setRequestFilterBlock:^(NSURLRequest* request) {
     EXPECT_TRUE(false) << "Block should not be called for unsupported requests";
     return YES;
   }];
   StartDataTaskAndWaitForCompletion(task);
   EXPECT_EQ(nil, [delegate_ error]);
   EXPECT_TRUE([[delegate_ responseBody] containsString:testString]);
 }
 
 }  // namespace cronet