Adjust URLFetcher::Create API so that object is returned as scoped_ptr.

ios/chrome/browser/net/retryable_url_fetcher.mm

Index: ios/chrome/browser/net/retryable_url_fetcher.mm
diff --git a/ios/chrome/browser/net/retryable_url_fetcher.mm b/ios/chrome/browser/net/retryable_url_fetcher.mm
index 0e6bc6050ea7ded70085d965983891d2000aa285..8269ca6df28d5b63d9a8b2c3b8b19340325a2365 100644
--- a/ios/chrome/browser/net/retryable_url_fetcher.mm
+++ b/ios/chrome/browser/net/retryable_url_fetcher.mm
@@ -58,8 +58,8 @@ class URLRequestDelegate : public net::URLFetcherDelegate {
   GURL url(base::SysNSStringToUTF8([delegate_ urlToFetch]));
   if (url.is_valid()) {
     fetcherDelegate_.reset(new URLRequestDelegate(self));
-    fetcher_.reset(net::URLFetcher::Create(url, net::URLFetcher::GET,
-                                           fetcherDelegate_.get()));
+    fetcher_ = net::URLFetcher::Create(url, net::URLFetcher::GET,
+                                       fetcherDelegate_.get());
     fetcher_->SetRequestContext(requestContextGetter_.get());
     fetcher_->Start();
   }