Add rappor::SampleString for consisntecy with domain+registry case

components/rappor/rappor_utils.h

 // Copyright 2015 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_RAPPOR_RAPPOR_UTILS_H_
 #define COMPONENTS_RAPPOR_RAPPOR_UTILS_H_
 
 #include <string>
 
+#include "components/rappor/rappor_service.h"
+
 class GURL;
 
 namespace rappor {
 
 class RapporService;
 
+// Records a string to a Rappor metric.
+// If |rappor_service| is NULL, this call does nothing.
+void SampleString(RapporService* rappor_service,
+                  const std::string& metric,
+                  RapporType type,
+                  const std::string& sample);
+
 // Extract the domain and registry for a sample from a GURL.
 // For file:// urls this will just return "file://" and for other special
 // schemes like chrome-extension will return the scheme and host.
 std::string GetDomainAndRegistrySampleFromGURL(const GURL& gurl);
 
 // Records the domain and registry of a url to a Rappor metric.
 // If |rappor_service| is NULL, this call does nothing.
 void SampleDomainAndRegistryFromGURL(RapporService* rappor_service,
                                      const std::string& metric,
                                      const GURL& gurl);
 
 }  // namespace rappor
 
 #endif  // COMPONENTS_RAPPOR_RAPPOR_UTILS_H_