Add variations params api to get params from features.

components/variations/variations_associated_data.h

Index: components/variations/variations_associated_data.h
diff --git a/components/variations/variations_associated_data.h b/components/variations/variations_associated_data.h
index 79f31a31e0516904de7f7a262a785d8742cdefdd..11af18d112fb59cacc8718227336c8dd0ad28b1a 100644
--- a/components/variations/variations_associated_data.h
+++ b/components/variations/variations_associated_data.h
@@ -41,6 +41,10 @@
 //   // use |id|
 // }
 
+namespace base {
+struct Feature;
+}
+
 namespace variations {
 
 typedef int VariationID;
@@ -123,6 +127,18 @@ bool AssociateVariationParams(const std::string& trial_name,
 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
@@ -133,6 +149,18 @@ bool GetVariationParams(const std::string& trial_name,
 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 {