[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 ca3a8998edfa2c48100f3ea4c35087c34c634767..fb71a09ef73022bd73a88496a7774a14b7ff9729 100644
--- a/components/cronet/ios/test/start_cronet.mm
+++ b/components/cronet/ios/test/start_cronet.mm
@@ -13,20 +13,17 @@
 
 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 setSslKeyLogFileName:@"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 setSslKeyLogFileName:@"SSLKEYLOGFILE"];
+  [Cronet addQuicHint:@"test.example.com" port:443 altPort:443];
+  [Cronet enableTestCertVerifierForTesting];
+
+  [Cronet start];
+
   NSString* rules = base::SysUTF8ToNSString(
       base::StringPrintf("MAP test.example.com 127.0.0.1:%d,"
                          "MAP notfound.example.com ~NOTFOUND",