[Media Router] Add DialMediaSinkService and DeviceDescriptionService

chrome/browser/media/router/discovery/dial/device_description_service.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 CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_DIAL_DEVICE_DESCRIPTION_SERVICE_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_DIAL_DEVICE_DESCRIPTION_SERVICE_H_
+
+#include <memory>
+#include <string>
+
+#include "base/callback.h"
+#include "base/threading/thread_checker.h"
+#include "base/timer/timer.h"
+#include "chrome/browser/media/router/discovery/dial/dial_device_data.h"
+#include "chrome/browser/media/router/discovery/dial/parsed_dial_device_description.h"
+#include "chrome/common/media_router/dial_device_description_parser.mojom.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace net {
+class URLRequestContextGetter;
+}
+
+namespace media_router {
+
+class DeviceDescriptionFetcher;
+class SafeDialDeviceDescriptionParser;
+
+// This class fetches and parses device description xml for DIAL devices. It

[mark a. foltz, 2017/04/18 18:16:26]

s/xml/XML/

[zhaobin, 2017/04/21 23:12:58]

Done.

+// lives on IO thread.

[mark a. foltz, 2017/04/18 18:16:26]

You might mention that the parsing happens in a separate utility process via
SafeDeviceDescriptionParser (instead of in this class).

[zhaobin, 2017/04/21 23:12:59]

Done.

+class DeviceDescriptionService {
+ public:
+  // Represents cached device description data parsed from device description
+  // XML.
+  struct CacheEntry {
+    CacheEntry();
+    CacheEntry(const CacheEntry& other);
+    ~CacheEntry();
+
+    // The expiration time from the cache.
+    base::Time expire_time;
+
+    // The version number.

[mark a. foltz, 2017/04/18 18:16:27]

The device description version number (non-negative)

[zhaobin, 2017/04/21 23:12:59]

Done.

+    int32_t config_id;
+
+    // Underlying device description data from XML.

[mark a. foltz, 2017/04/18 18:16:26]

s/Underlying/Parsed/

[zhaobin, 2017/04/21 23:12:58]

Done.

+    ParsedDialDeviceDescription description_data;
+  };
+
+  // Called if parsing device description XML in utility process succeeds, and
+  // all fields are valid.
+  // |device_data|: The device to look up.
+  // |description_data|: Device description data from device description XML.
+  using DeviceDescriptionParseSuccessCallback =
+      base::Callback<void(const DialDeviceData& device_data,
+                          const ParsedDialDeviceDescription& description_data)>;
+
+  // Called if parsing device description XML in utility process fails, or some
+  // parsed fields are missing or invalid.
+  using DeviceDescriptionParseErrorCallback =
+      base::Callback<void(const DialDeviceData& device_data,
+                          const std::string& error_message)>;
+
+  DeviceDescriptionService(
+      const DeviceDescriptionParseSuccessCallback& success_cb,
+      const DeviceDescriptionParseErrorCallback& error_cb);
+  virtual ~DeviceDescriptionService();
+
+  // For each device in |devices|, if there is a valid cache entry for it, call
+  // |success_cb_| with cached device description; otherwise start fetching
+  // device description XML and parsing XML in utility process. Call
+  // |success_cb_| if both fetching and parsing succeeds; otherwise call
+  // |error_cb_|.
+  // |request_context|: Used by the background URLFetchers.
+  virtual void GetDeviceDescriptions(
+      const std::vector<DialDeviceData>& devices,
+      net::URLRequestContextGetter* request_context);
+
+  // Remove expired cache entry from |description_map_|.

[mark a. foltz, 2017/04/18 18:16:26]

s/entry/entries/

[zhaobin, 2017/04/21 23:12:59]

Done.

+  void CleanUpCacheEntries();
+
+ protected:
+  virtual base::Time GetNow();
+
+ private:
+  // Checks the cache for a valid device description. If the entry is found but
+  // is no longer valid, it is removed from the cache. Ruturns cached entry of

[mark a. foltz, 2017/04/18 18:16:26]

s/is no longer valid/is expired/

Typo in Returns

[zhaobin, 2017/04/21 23:12:59]

Done.

+  // parsed device description. Returns nullptr if cache entry does not exist or
+  // is not valid.
+  // |device_data|: The device to look up.
+  const CacheEntry* CheckAndUpdateCache(const DialDeviceData& device_data);
+
+  // Issues a HTTP GET request for the device description. No-op if there is
+  // already a pending request.
+  // |device_data|: The device to look up.

[mark a. foltz, 2017/04/18 18:16:27]

Nit: document |request_context|

[zhaobin, 2017/04/21 23:12:58]

Done.

+  void FetchDeviceDescription(const DialDeviceData& device_data,
+                              net::URLRequestContextGetter* request_context);
+
+  // Invoked when HTTP GET request finishes.
+  // |device_data|: Device data initiating the HTTP request.
+  // |description_data|: Response from HTTP request.
+  void OnDeviceDescriptionFetchComplete(
+      const DialDeviceData& device_data,
+      const DialDeviceDescriptionData& description_data);
+
+  // Invoked when HTTP GET request fails.
+  // |device_data|: Device data initiating the HTTP request.

[mark a. foltz, 2017/04/18 18:16:26]

Nit: document |error_message|

[zhaobin, 2017/04/21 23:12:59]

Done.

+  void OnDeviceDescriptionFetchError(const DialDeviceData& device_data,
+                                     const std::string& error_message);
+
+  // Invoked when SafeDialDeviceDescriptionParser finishes parsing device
+  // description XML.
+  // |device_data|: Device data initiating XML parsing in utility process.
+  // |app_url|: The app Url.
+  // |device_description_ptr|: Parsed device description from utility process.
+  // Returns nullptr if parsing fails.
+  void OnParsedDeviceDescription(
+      const DialDeviceData& device_data,
+      const GURL& app_url,
+      chrome::mojom::DialDeviceDescriptionPtr device_description_ptr);
+
+  // Map of <device label, DeviceDescriptionFetcher>

[mark a. foltz, 2017/04/18 18:16:27]

Document the meaning of the entries, e.g. "Map of current device description
fetches in progress."

[zhaobin, 2017/04/21 23:12:59]

Done.

+  std::map<std::string, std::unique_ptr<DeviceDescriptionFetcher>>
+      device_description_fetcher_map_;
+
+  // Map of <device label, CacheEntry>
+  std::map<std::string, CacheEntry> description_map_;
+
+  // See comments for DeviceDescriptionParseSuccessCallback.
+  DeviceDescriptionParseSuccessCallback success_cb_;
+
+  // See comments for DeviceDescriptionParseErrorCallback.
+  DeviceDescriptionParseErrorCallback error_cb_;
+
+  // Timer for clean up expired cache entries.
+  std::unique_ptr<base::RepeatingTimer,
+                  content::BrowserThread::DeleteOnIOThread>
+      clean_up_timer_;
+
+  // Safe DIAL parser associated with utility process.
+  scoped_refptr<SafeDialDeviceDescriptionParser> parser_;
+
+  base::ThreadChecker thread_checker_;
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_DIAL_DEVICE_DESCRIPTION_SERVICE_H_