Add a mechanism to force parameters of a group to a specific value.

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 95 matching lines @@
                                            const ActiveGroupId& active_group);
 
 // Associates the specified set of key-value |params| with the variation
 // specified by |trial_name| and |group_name|. Fails and returns false if the
 // specified variation already has params associated with it or the field trial
 // is already active (group() has been called on it). Thread safe.
 bool AssociateVariationParams(const std::string& trial_name,
                               const std::string& group_name,
                               const std::map<std::string, std::string>& params);
 
+// TODO: describe string formating
+// TrialName1.GroupName1.Key1/Value1/TrialName2.GroupName2.Key2/Value2/

[Alexei Svitkine (slow), 2015/04/22 15:42:37]

How about trial.group.key/value/key/value,trial.group:k/v,k/v,

that way, we don't have to repeat trial/group names if there are a lot of params
for the same group.

[Alexei Svitkine (slow), 2015/04/24 16:17:26]

(Oops, realise above is inconsistent, meant
trial.group.key/value/key/value,trial.group:k/v/k/v,...

[danduong, 2015/04/24 16:22:08]

I'm still confused.

do you mean:
trial1.group1:k1/v1/k2/v2,trail2.group2:k1/v1/k2/v2/k3/v3,..

[Alexei Svitkine (slow), 2015/04/24 16:31:52]

Yes, sorry for not being very clear before.

+bool AssociateParamsFromString(const std::string&);
+
 // 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);
 
@@ skipping 14 matching lines @@
 void ClearAllVariationIDs();
 
 // Clears all of the associated params.
 void ClearAllVariationParams();
 
 }  // namespace testing
 
 }  // namespace variations
 
 #endif  // COMPONENTS_VARIATIONS_VARIATIONS_ASSOCIATED_DATA_H_