Move ranker_model_loader to a new component.

components/ranker/ranker_url_fetcher.h

+// 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.
+
+#ifndef COMPONENTS_RANKER_TRANSLATE_URL_FETCHER_H_
+#define COMPONENTS_RANKER_TRANSLATE_URL_FETCHER_H_
+
+#include <memory>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "net/url_request/url_fetcher_delegate.h"
+#include "url/gurl.h"
+
+namespace ranker {
+
+// Downloads Ranker models.
+class RankerURLFetcher : public net::URLFetcherDelegate {
+ public:
+  // Callback type for Request().
+  typedef base::Callback<void(bool, const std::string&)> Callback;
+
+  // Represents internal state if the fetch is completed successfully.
+  enum State {
+    IDLE,        // No fetch request was issued.
+    REQUESTING,  // A fetch request was issued, but not finished yet.
+    COMPLETED,   // The last fetch request was finished successfully.
+    FAILED,      // The last fetch request was finished with a failure.
+  };
+
+  explicit RankerURLFetcher();
+  ~RankerURLFetcher() override;
+
+  int max_retry_on_5xx() { return max_retry_on_5xx_; }
+  void set_max_retry_on_5xx(int count) { max_retry_on_5xx_ = count; }
+
+  // Requests to |url|. |callback| will be invoked when the function returns
+  // true, and the request is finished asynchronously.
+  // Returns false if the previous request is not finished, or the request
+  // is omitted due to retry limitation.
+  bool Request(const GURL& url, const Callback& callback);
+
+  // Gets internal state.
+  State state() { return state_; }
+
+  // net::URLFetcherDelegate implementation:
+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+ private:
+  // URL to send the request.
+  GURL url_;
+
+  // Internal state.
+  enum State state_;
+
+  // URLFetcher instance.
+  std::unique_ptr<net::URLFetcher> fetcher_;
+
+  // Callback passed at Request(). It will be invoked when an asynchronous
+  // fetch operation is finished.
+  Callback callback_;
+
+  // Counts how many times did it try to fetch the language list.
+  int retry_count_;
+
+  // Max number how many times to retry on the server error
+  int max_retry_on_5xx_;
+
+  DISALLOW_COPY_AND_ASSIGN(RankerURLFetcher);
+};
+
+}  // namespace ranker
+
+#endif  // COMPONENTS_RANKER_TRANSLATE_URL_FETCHER_H_