RemoteSuggestionsFetcher: Use common AccessTokenFetcher helper class

components/ntp_snippets/remote/remote_suggestions_fetcher_unittest.cc

 // Copyright 2016 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 "components/ntp_snippets/remote/remote_suggestions_fetcher.h"
 
 #include <deque>
 #include <map>
 #include <utility>
 #include <vector>
@@ skipping 381 matching lines @@
 };
 
 class RemoteSuggestionsSignedOutFetcherTest
     : public RemoteSuggestionsFetcherTestBase {
  public:
   RemoteSuggestionsSignedOutFetcherTest()
       : RemoteSuggestionsFetcherTestBase(
             GURL(kTestChromeContentSuggestionsSignedOutUrl)) {}
 };
 
-// TODO(jkrcal): Add unit-tests for the "authentication in progress" case as it
-// requires more changes (instead FakeSigninManagerBase use FakeSigninManager
-// which does not exist on ChromeOS). crbug.com/688310
+// TODO(jkrcal): Investigate whether the "authentication in progress" case can
+// ever happen (see discussion on https://codereview.chromium.org/2582573002),
+// and if so, add unit-tests for it. This will require more changes (instead of
+// FakeSigninManagerBase use FakeSigninManager which does not exist on
+// ChromeOS). crbug.com/688310
 class RemoteSuggestionsSignedInFetcherTest
     : public RemoteSuggestionsFetcherTestBase {
  public:
   RemoteSuggestionsSignedInFetcherTest()
       : RemoteSuggestionsFetcherTestBase(
             GURL(kTestChromeContentSuggestionsSignedInUrl)) {}
 };
 
 TEST_F(RemoteSuggestionsSignedOutFetcherTest, ShouldNotFetchOnCreation) {
   // The lack of registered baked in responses would cause any fetch to fail.
@@ skipping 574 matching lines @@
         fetched_categories) {
   if (fetched_categories) {
     // Matchers above aren't any more precise than this, so this is sufficient
     // for test-failure diagnostics.
     return os << "list with " << fetched_categories->size() << " elements";
   }
   return os << "null";
 }
 
 }  // namespace ntp_snippets