Shift cookie system callbacks to OnceCallback to impedance match mojo.

ios/net/cookies/cookie_store_ios_test_util.mm

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ios/net/cookies/cookie_store_ios_test_util.h"
 
 #import <Foundation/Foundation.h>
 
 #include "base/memory/ptr_util.h"
 #include "base/run_loop.h"
@@ skipping 62 matching lines @@
 
 void TestPersistentCookieStore::AddCookie(const net::CanonicalCookie& cc) {}
 
 void TestPersistentCookieStore::UpdateCookieAccessTime(
     const net::CanonicalCookie& cc) {}
 
 void TestPersistentCookieStore::DeleteCookie(const net::CanonicalCookie& cc) {}
 
 void TestPersistentCookieStore::SetForceKeepSessionState() {}
 
-void TestPersistentCookieStore::Flush(const base::Closure& callback) {
+void TestPersistentCookieStore::Flush(base::OnceClosure callback) {
   flushed_ = true;
 }
 
 #pragma mark -
 #pragma mark GetCookieCallback
 
 GetCookieCallback::GetCookieCallback() : did_run_(false) {}
 
 #pragma mark -
 #pragma mark GetCookieCallback methods
@@ skipping 39 matching lines @@
 void ClearCookies() {
   NSHTTPCookieStorage* store = [NSHTTPCookieStorage sharedHTTPCookieStorage];
   [store setCookieAcceptPolicy:NSHTTPCookieAcceptPolicyAlways];
   NSArray* cookies = [store cookies];
   for (NSHTTPCookie* cookie in cookies)
     [store deleteCookie:cookie];
   EXPECT_EQ(0u, [[store cookies] count]);
 }
 
 }  // namespace net