Add an IPC method for Blink to call RapporService::RecordSample()

base/metrics/user_metrics.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 BASE_METRICS_USER_METRICS_H_
 #define BASE_METRICS_USER_METRICS_H_
 
 #include <string>
 
 #include "base/base_export.h"
@@ skipping 30 matching lines @@
 // possible actions), see RecordComputedAction.
 BASE_EXPORT void RecordAction(const UserMetricsAction& action);
 
 // This function has identical input and behavior to RecordAction, but is
 // not automatically found by the action-processing scripts.  It can be used
 // when it's a pain to enumerate all possible actions, but if you use this
 // you need to also update the rules for extracting known actions in
 // tools/metrics/actions/extract_actions.py.
 BASE_EXPORT void RecordComputedAction(const std::string& action);
 
+// This function records a sample string along with the metric using RAPPOR.
+BASE_EXPORT void RecordRappor(
+    const std::string& metric,
+    const std::string& sample);

[Ilya Sherman, 2015/03/25 20:51:02]

RAPPOR is not a concept that current exists in base.  I'm not really convinced
that it's appropriate to add it here.  But, if we do decide that //base is the
right place to add it, please create a new file for it.  The user_metrics files
are for user actions, not for all UMA metrics.  (I do realize that the name is
somewhat confusing :/)

+
 // Called with the action string.
 typedef base::Callback<void(const std::string&)> ActionCallback;
 
 // Add/remove action callbacks (see above).
 BASE_EXPORT void AddActionCallback(const ActionCallback& callback);
 BASE_EXPORT void RemoveActionCallback(const ActionCallback& callback);
 
+typedef base::Callback<void(
+    const std::string&,
+    const std::string&)> RapporCallback;
+
+BASE_EXPORT void AddRapporCallback(const RapporCallback& callback);
+
 }  // namespace base
 
 #endif  // BASE_METRICS_USER_METRICS_H_