Revert of ios: Remove use of MessageLoopProxy and deprecated MessageLoop APIs

ios/chrome/browser/net/retryable_url_fetcher_unittest.mm

Index: ios/chrome/browser/net/retryable_url_fetcher_unittest.mm
diff --git a/ios/chrome/browser/net/retryable_url_fetcher_unittest.mm b/ios/chrome/browser/net/retryable_url_fetcher_unittest.mm
index 9c8f48b19d039c1d21854c1c31157393f82fc6e6..6f73234ca6aceb33975fb1da84dd50adde3a6359 100644
--- a/ios/chrome/browser/net/retryable_url_fetcher_unittest.mm
+++ b/ios/chrome/browser/net/retryable_url_fetcher_unittest.mm
@@ -60,7 +60,7 @@
 
 TEST_F(RetryableURLFetcherTest, TestResponse200) {
   scoped_refptr<net::URLRequestContextGetter> request_context_getter =
-      new net::TestURLRequestContextGetter(message_loop_.task_runner());
+      new net::TestURLRequestContextGetter(message_loop_.message_loop_proxy());
   base::scoped_nsobject<RetryableURLFetcher> retryableFetcher(
       [[RetryableURLFetcher alloc]
           initWithRequestContextGetter:request_context_getter.get()
@@ -81,7 +81,7 @@
 
 TEST_F(RetryableURLFetcherTest, TestResponse404) {
   scoped_refptr<net::URLRequestContextGetter> request_context_getter =
-      new net::TestURLRequestContextGetter(message_loop_.task_runner());
+      new net::TestURLRequestContextGetter(message_loop_.message_loop_proxy());
   base::scoped_nsobject<RetryableURLFetcher> retryableFetcher(
       [[RetryableURLFetcher alloc]
           initWithRequestContextGetter:request_context_getter.get()