chromeos: remove static modifier in ToString func

chrome/browser/chromeos/dbus/power_manager_client.h

 // Copyright (c) 2011 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_CHROMEOS_DBUS_POWER_MANAGER_CLIENT_H_
 #define CHROME_BROWSER_CHROMEOS_DBUS_POWER_MANAGER_CLIENT_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 12 matching lines @@
   bool battery_is_present;
   bool battery_is_full;
 
   // Time in seconds until the battery is empty or full, 0 for unknown.
   int64 battery_seconds_to_empty;
   int64 battery_seconds_to_full;
 
   double battery_percentage;
 
   PowerSupplyStatus();
-  const std::string& ToString() const;
+  std::string ToString() const;
 };
 
 // Callback used for processing the idle time.  The int64 param is the number of
 // seconds the user has been idle.
 typedef base::Callback<void(int64)> CalculateIdleTimeCallback;
 
 // PowerManagerClient is used to communicate with the power manager.
 class PowerManagerClient {
  public:
   // Interface for observing changes from the power manager.
@@ skipping 43 matching lines @@
   // Create() should be used instead.
   PowerManagerClient();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PowerManagerClient);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_DBUS_POWER_MANAGER_CLIENT_H_