[NTP Snippets] Add unit tests for NTPSnippetsFetcher

components/ntp_snippets/ntp_snippets_fetcher.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/ntp_snippets_fetcher.h"
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/path_service.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 68 matching lines @@
 
 NTPSnippetsFetcher::~NTPSnippetsFetcher() {}
 
 std::unique_ptr<NTPSnippetsFetcher::SnippetsAvailableCallbackList::Subscription>
 NTPSnippetsFetcher::AddCallback(const SnippetsAvailableCallback& callback) {
   return callback_list_.Add(callback);
 }
 
 void NTPSnippetsFetcher::FetchSnippets(const std::set<std::string>& hosts,
                                        int count) {
-  // TODO(treib): What to do if there's already a pending request?
   const std::string& key = is_stable_channel_
                                ? google_apis::GetAPIKey()
                                : google_apis::GetNonStableAPIKey();
   std::string url =
       base::StringPrintf(kContentSnippetsServerFormat, key.c_str());
   url_fetcher_ = URLFetcher::Create(GURL(url), URLFetcher::POST, this);
+  CHECK(url_fetcher_ != nullptr);

[Marc Treib, 2016/05/03 11:33:42]

DCHECK please (DCHECKS are enabled on all the bots, so it'll still get
exercised).
Also the "!= nullptr" isn't required, and is usually omitted in Chromium.

[mastiz, 2016/05/03 11:48:57]

Done. Removed, as discussed offline.

   url_fetcher_->SetRequestContext(url_request_context_getter_.get());
   url_fetcher_->SetLoadFlags(net::LOAD_DO_NOT_SEND_COOKIES |
                              net::LOAD_DO_NOT_SAVE_COOKIES);
   HttpRequestHeaders headers;
   headers.SetHeader("Content-Type", "application/json; charset=UTF-8");
   url_fetcher_->SetExtraRequestHeaders(headers.ToString());
   std::string host_restricts;
   for (const std::string& host : hosts)
     host_restricts += base::StringPrintf(kHostRestrictFormat, host.c_str());
   url_fetcher_->SetUploadData("application/json",
@@ skipping 30 matching lines @@
 
   } else {
     bool stores_result_to_string = source->GetResponseAsString(&response);
     DCHECK(stores_result_to_string);
   }
 
   callback_list_.Notify(response, message);
 }
 
 }  // namespace ntp_snippets