[cronet] Add mechanism for restarting CronetEnvironment

components/cronet/ios/test/start_cronet.mm

Index: components/cronet/ios/test/start_cronet.mm
diff --git a/components/cronet/ios/test/start_cronet.mm b/components/cronet/ios/test/start_cronet.mm
index f7eee77187485b2455912793d66a685f8d367c76..6431ecf84ecdf31bc72bc5e47492ae748643f077 100644
--- a/components/cronet/ios/test/start_cronet.mm
+++ b/components/cronet/ios/test/start_cronet.mm
@@ -13,25 +13,22 @@
 
 namespace cronet {
 
-void StartCronetIfNecessary(int port) {
-  static bool initialized = false;
-  if (!initialized) {
-    initialized = true;
-    [Cronet setUserAgent:@"CronetTest/1.0.0.0" partial:NO];
-    [Cronet setHttp2Enabled:true];
-    [Cronet setQuicEnabled:true];
-    [Cronet setAcceptLanguages:@"en-US,en"];
-    [Cronet
-        setExperimentalOptions:
-            [NSString
-                stringWithFormat:@"{\"ssl_key_log_file\":\"%@\"}",
-                                 [Cronet
-                                     getNetLogPathForFile:@"SSLKEYLOGFILE"]]];
-    [Cronet addQuicHint:@"test.example.com" port:443 altPort:443];
-    [Cronet enableTestCertVerifierForTesting];
-    [Cronet setHttpCacheType:CRNHttpCacheTypeDisabled];
-    [Cronet start];
-  }
+void StartCronet(int port) {
+  [Cronet setUserAgent:@"CronetTest/1.0.0.0" partial:NO];
+  [Cronet setHttp2Enabled:true];
+  [Cronet setQuicEnabled:true];
+  [Cronet setAcceptLanguages:@"en-US,en"];
+  [Cronet
+      setExperimentalOptions:
+          [NSString
+              stringWithFormat:@"{\"ssl_key_log_file\":\"%@\"}",
+                               [Cronet getNetLogPathForFile:@"SSLKEYLOGFILE"]]];
+  [Cronet addQuicHint:@"test.example.com" port:443 altPort:443];
+  [Cronet enableTestCertVerifierForTesting];
+  [Cronet setHttpCacheType:CRNHttpCacheTypeDisabled];
+
+  [Cronet start];
+
   NSString* rules = base::SysUTF8ToNSString(
       base::StringPrintf("MAP test.example.com 127.0.0.1:%d,"
                          "MAP notfound.example.com ~NOTFOUND",