Add variations params api to get params from features.

components/variations/variations_associated_data.h

 // Copyright 2013 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_VARIATIONS_VARIATIONS_ASSOCIATED_DATA_H_
 #define COMPONENTS_VARIATIONS_VARIATIONS_ASSOCIATED_DATA_H_
 
 #include <map>
 #include <string>
 
@@ skipping 23 matching lines @@
 //
 //  std::string value = GetVariationParamValue("trial", "param_x");
 //  // use |value|, which will be "" if it does not exist
 //
 // VariationID id = GetGoogleVariationID(GOOGLE_WEB_PROPERTIES, "trial",
 //                                       "group1");
 // if (id != variations::kEmptyID) {
 //   // use |id|
 // }
 
+namespace base {
+struct Feature;
+}
+
 namespace variations {
 
 typedef int VariationID;
 
 const VariationID EMPTY_ID = 0;
 
 // A key into the Associate/Get methods for VariationIDs. This is used to create
 // separate ID associations for separate parties interested in VariationIDs.
 enum IDCollectionKey {
   // This collection is used by Google web properties, transmitted through the
@@ skipping 62 matching lines @@
 // Retrieves the set of key-value |params| for the variation associated with
 // the specified field trial, based on its selected group. If the field trial
 // does not exist or its selected group does not have any parameters associated
 // with it, returns false and does not modify |params|. Calling this function
 // will result in the field trial being marked as active if found (i.e. group()
 // will be called on it), if it wasn't already. Currently, this information is
 // only available from the browser process. Thread safe.
 bool GetVariationParams(const std::string& trial_name,
                         std::map<std::string, std::string>* params);
 
+// Retvieves the set of key-value |params| for the variation associated with the

[Alexei Svitkine (slow), 2016/05/03 17:04:25]

Nit: Retrieves

[jwd, 2016/05/03 20:12:27]

Done.

+// specified |feature|. A feature is associated with at most one variation,
+// through the variation's associated field trial, and selected group. See
+// base/feature_list.h for more information on features. If the feature is not
+// enabled, or if there's no associated variation params, returns false and does
+// not modify |params|. Calling this function will result in the associated
+// field trial being marked as active if found (i.e. group() will be called on
+// it), if it wasn't already. Currently, this information is only available from
+// the browser process. Thread safe.
+bool GetVariationParamsByFeature(const base::Feature& feature,
+                                 std::map<std::string, std::string>* params);
+
 // Retrieves a specific parameter value corresponding to |param_name| for the
 // variation associated with the specified field trial, based on its selected
 // group. If the field trial does not exist or the specified parameter does not
 // exist, returns an empty string. Calling this function will result in the
 // field trial being marked as active if found (i.e. group() will be called on
 // it), if it wasn't already. Currently, this information is only available from
 // the browser process. Thread safe.
 std::string GetVariationParamValue(const std::string& trial_name,
                                    const std::string& param_name);
 
+// Retrieves a specific parameter value corresponding to |param_name| for the
+// variation associated with the specified |feature|. A feature is associated
+// with at most one variation, through the variation's associated field trial,
+// and selected group. See base/feature_list.h for more information on
+// features. If the feature is not enabled, or if there's no associated
+// variation params, returns false and does not modify |params|. Calling this
+// function will result in the associated field trial being marked as active if
+// found (i.e. group() will be called on it), if it wasn't already. Currently,
+// this information is only available from the browser process. Thread safe.
+std::string GetVariationParamValueByFeature(const base::Feature& feature,
+                                            const std::string& param_name);
+
 // Expose some functions for testing.
 namespace testing {
 
 // Clears all of the mapped associations.
 void ClearAllVariationIDs();
 
 // Clears all of the associated params.
 void ClearAllVariationParams();
 
 }  // namespace testing
 
 }  // namespace variations
 
 #endif  // COMPONENTS_VARIATIONS_VARIATIONS_ASSOCIATED_DATA_H_