Extend LargeIconService to fetch missing favicons from a Google server

ios/chrome/app/spotlight/spotlight_manager_unittest.mm

 // Copyright 2015 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 <memory>
 
 #import <CoreSpotlight/CoreSpotlight.h>
 #import <Foundation/Foundation.h>
 
 #include "base/location.h"
@@ skipping 49 matching lines @@
   result.icon_type = favicon_base::TOUCH_ICON;
   CHECK(result.is_valid());
   return result;
 }
 
 class SpotlightManagerTest : public testing::Test {
  protected:
   SpotlightManagerTest() {
     model_ = bookmarks::TestBookmarkClient::CreateModel();
     large_icon_service_.reset(new favicon::LargeIconService(
-        &mock_favicon_service_, base::ThreadTaskRunnerHandle::Get()));
+        &mock_favicon_service_, base::ThreadTaskRunnerHandle::Get(),
+        /*image_fetcher=*/nullptr));
     bookmarksSpotlightManager_ = [[BookmarksSpotlightManager alloc]
         initWithLargeIconService:large_icon_service_.get()
                    bookmarkModel:model_.get()];
 
     EXPECT_CALL(mock_favicon_service_,
                 GetLargestRawFaviconForPageURL(_, _, _, _, _))
         .WillRepeatedly(PostReply<5>(CreateTestBitmap(24, 24)));
   }
 
   base::MessageLoop loop_;
@@ skipping 85 matching lines @@
   NSSet* spotlightManagerKeywords =
       [NSSet setWithArray:[[item attributeSet] keywords]];
   EXPECT_TRUE([spotlightManagerKeywords count] > 0);
   // Check static/hardcoded keywords exist
   NSSet* hardCodedKeywordsSet =
       [NSSet setWithArray:ios::GetChromeBrowserProvider()
                               ->GetSpotlightProvider()
                               ->GetAdditionalKeywords()];
   EXPECT_TRUE([hardCodedKeywordsSet isSubsetOfSet:spotlightManagerKeywords]);
 }