[Doodle] Allow overriding the API URL via a fieldtrial param

components/doodle/doodle_fetcher_impl.h

 // 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.
 
 #ifndef COMPONENTS_DOODLE_DOODLE_FETCHER_IMPL_H_
 #define COMPONENTS_DOODLE_DOODLE_FETCHER_IMPL_H_
 
 #include <memory>
 #include <string>
 #include <utility>
@@ skipping 28 matching lines @@
   // Callback for JSON parsing to allow injecting platform-dependent code.
   using ParseJSONCallback = base::Callback<void(
       const std::string& unsafe_json,
       const base::Callback<void(std::unique_ptr<base::Value> json)>& success,
       const base::Callback<void(const std::string&)>& error)>;
 
   DoodleFetcherImpl(
       scoped_refptr<net::URLRequestContextGetter> download_context,
       GoogleURLTracker* google_url_tracker,
       const ParseJSONCallback& json_parsing_callback,
-      bool gray_background);
+      bool gray_background,
+      const base::Optional<std::string>& override_url);
   ~DoodleFetcherImpl() override;
 
   // Fetches a doodle asynchronously. The |callback| is called with a
   // DoodleState indicating whether the request succeded in fetching a doodle.
   // If a fetch is already running, the callback will be queued and invoked with
   // result from the next completed request.
   void FetchDoodle(FinishedCallback callback) override;
 
  private:
   // net::URLFetcherDelegate implementation.
@@ skipping 16 matching lines @@
 
   // Returns whether a fetch is still in progress. A fetch begins when a
   // callback is added and ends when the last callback was called.
   bool IsFetchInProgress() const { return !callbacks_.empty(); }
 
   // Parameters set from constructor.
   scoped_refptr<net::URLRequestContextGetter> const download_context_;
   GoogleURLTracker* google_url_tracker_;
   ParseJSONCallback json_parsing_callback_;
   const bool gray_background_;
+  const base::Optional<std::string> override_url_;
 
   std::vector<FinishedCallback> callbacks_;
   std::unique_ptr<net::URLFetcher> fetcher_;
 
   base::WeakPtrFactory<DoodleFetcherImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DoodleFetcherImpl);
 };
 
 }  // namespace doodle
 
 #endif  // COMPONENTS_DOODLE_DOODLE_FETCHER_IMPL_H_