Use IOSImageDataFetcherWrapper for favicon

ios/web/public/test/fakes/test_web_state.mm

 // Copyright 2014 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.
 
 #import "ios/web/public/test/fakes/test_web_state.h"
 
 #include <stdint.h>
 
 #include "base/callback.h"
 #include "ios/web/public/web_state/web_state_observer.h"
@@ skipping 165 matching lines @@
 }
 
 void TestWebState::SetTrustLevel(URLVerificationTrustLevel trust_level) {
   trust_level_ = trust_level;
 }
 
 CRWWebViewProxyType TestWebState::GetWebViewProxy() const {
   return nullptr;
 }
 
-int TestWebState::DownloadImage(const GURL& url,
-                                bool is_favicon,
-                                uint32_t max_bitmap_size,
-                                bool bypass_cache,
-                                const ImageDownloadCallback& callback) {
-  return 0;
-}
-
 service_manager::InterfaceRegistry* TestWebState::GetMojoInterfaceRegistry() {
   return nullptr;
 }
 
 base::WeakPtr<WebState> TestWebState::AsWeakPtr() {
   NOTREACHED();
   return base::WeakPtr<WebState>();
 }
 
 }  // namespace web