Support RCTNetworking#clearCookies on iOS

Summary:
This adds cookie clearing support for iOS to match the existing support on Android.  Helpful for resetting the app to a clean state (say, when logging a user out).
Closes https://github.com/facebook/react-native/pull/9264

Differential Revision: D3776492

Pulled By: javache

fbshipit-source-id: 59ae19ac09d3cf0d0e229cd9e8e30865e65ca96c

Examples/UIExplorer/js/XHRExample.ios.js

@@ -41,6 +41,7 @@ var {
 var XHRExampleHeaders = require('./XHRExampleHeaders');
 var XHRExampleFetch = require('./XHRExampleFetch');
 var XHRExampleOnTimeOut = require('./XHRExampleOnTimeOut');
+var XHRExampleCookies = require('./XHRExampleCookies');
 
 /**
  * Convert number of bytes to MB and round to the nearest 0.1 MB.
@@ -432,6 +433,11 @@ exports.examples = [{
   render() {
     return <XHRExampleOnTimeOut/>;
   }
+}, {
+  title: 'Cookies',
+  render() {
+    return <XHRExampleCookies />;
+  }
 }];
 
 var styles = StyleSheet.create({

Libraries/Network/RCTNetworking.ios.js

@@ -52,7 +52,7 @@ class RCTNetworking extends NativeEventEmitter {
   }
 
   clearCookies(callback: (result: boolean) => any) {
-    console.warn('RCTNetworking.clearCookies is not supported on iOS');
+    RCTNetworkingNative.clearCookies(callback);
   }
 }
 

Libraries/Network/RCTNetworking.m

@@ -504,6 +504,20 @@ RCT_EXPORT_METHOD(abortRequest:(nonnull NSNumber *)requestID)
   [_tasksByRequestID removeObjectForKey:requestID];
 }
 
+RCT_EXPORT_METHOD(clearCookies:(RCTResponseSenderBlock)responseSender)
+{
+  NSHTTPCookieStorage *storage = [NSHTTPCookieStorage sharedHTTPCookieStorage];
+  if (!storage.cookies.count) {
+    responseSender(@[@NO]);
+    return;
+  }
+
+  for (NSHTTPCookie *cookie in storage.cookies) {
+    [storage deleteCookie:cookie];
+  }
+  responseSender(@[@YES]);
+}
+
 @end
 
 @implementation RCTBridge (RCTNetworking)