Shift cookie system callbacks to OnceCallback to impedance match mojo.

ios/net/cookies/cookie_store_ios_unittest.mm

Index: ios/net/cookies/cookie_store_ios_unittest.mm
diff --git a/ios/net/cookies/cookie_store_ios_unittest.mm b/ios/net/cookies/cookie_store_ios_unittest.mm
index 514738bd01e8795d3fc2c7ad4dec594e1826ec5d..bcaf08e0ed9f25342f42353644e247a8519db87e 100644
--- a/ios/net/cookies/cookie_store_ios_unittest.mm
+++ b/ios/net/cookies/cookie_store_ios_unittest.mm
@@ -96,10 +96,11 @@ class CookieStoreIOSTest : public testing::Test {
   ~CookieStoreIOSTest() override {}
 
   // Gets the cookies. |callback| will be called on completion.
-  void GetCookies(const net::CookieStore::GetCookiesCallback& callback) {
+  void GetCookies(net::CookieStore::GetCookiesCallback callback) {
     net::CookieOptions options;
     options.set_include_httponly();
-    store_->GetCookiesWithOptionsAsync(kTestCookieURL, options, callback);
+    store_->GetCookiesWithOptionsAsync(kTestCookieURL, options,
+                                       std::move(callback));
   }
 
   // Sets a cookie.