Add support to update_engine_client for -app_version and -omaha_url.

update_attempter.h

 // Copyright (c) 2010 The Chromium OS 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 CHROMEOS_PLATFORM_UPDATE_ENGINE_UPDATE_ATTEMPTER_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_UPDATE_ATTEMPTER_H__
 
 #include <time.h>
 #include <tr1/memory>
 #include <string>
@@ skipping 33 matching lines @@
         status_(UPDATE_STATUS_IDLE),
         download_progress_(0.0),
         last_checked_time_(0),
         new_version_("0.0.0.0"),
         new_size_(0) {
     last_notify_time_.tv_sec = 0;
     last_notify_time_.tv_nsec = 0;
     if (utils::FileExists(kUpdateCompletedMarker))
       status_ = UPDATE_STATUS_UPDATED_NEED_REBOOT;
   }
-  void Update();
+  // Checks for update and, if a newer version is available, attempts
+  // to update the system. Non-empty |in_app_version| or
+  // |in_update_url| prevents automatic detection of the parameter.
+  void Update(const std::string& app_version, const std::string& omaha_url);
 
   // ActionProcessorDelegate methods:
   void ProcessingDone(const ActionProcessor* processor, ActionExitCode code);
   void ProcessingStopped(const ActionProcessor* processor);
   void ActionCompleted(ActionProcessor* processor,
                        AbstractAction* action,
                        ActionExitCode code);
 
   // Stop updating. An attempt will be made to record status to the disk
   // so that updates can be resumed later.
   void Terminate();
 
   // Try to resume from a previously Terminate()d update.
   void ResumeUpdating();
 
   // Returns the current status in the out params. Returns true on success.
   bool GetStatus(int64_t* last_checked_time,
                  double* progress,
                  std::string* current_operation,
                  std::string* new_version,
                  int64_t* new_size);
 
   void set_dbus_service(struct UpdateEngineService* dbus_service) {
     dbus_service_ = dbus_service;
   }
 
-  void CheckForUpdate();
+  // This is the D-Bus service entry point for going through an
+  // update. If the current status is idle invokes Update.
+  void CheckForUpdate(const std::string& app_version,
+                      const std::string& omaha_url);
 
   // DownloadActionDelegate method
   void BytesReceived(uint64_t bytes_received, uint64_t total);
 
  private:
   // Sets the status to the given status and notifies a status update
   // over dbus.
   void SetStatusAndNotify(UpdateStatus status);
 
   // Creates an error event object in |error_event_| to be included in
@@ skipping 33 matching lines @@
 
   // Device paramaters common to all Omaha requests.
   OmahaRequestDeviceParams omaha_request_params_;
 
   DISALLOW_COPY_AND_ASSIGN(UpdateAttempter);
 };
 
 }  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_UPDATE_ATTEMPTER_H__