Add simpler API for changing parameters in tests.

components/variations/variations_associated_data.cc

Index: components/variations/variations_associated_data.cc
diff --git a/components/variations/variations_associated_data.cc b/components/variations/variations_associated_data.cc
index 9aa51d379f3d884a094d208d621e0d4eaacbe7f8..d7dda4b97d188a4c208e11ab5f35ba86551cdb94 100644
--- a/components/variations/variations_associated_data.cc
+++ b/components/variations/variations_associated_data.cc
@@ -16,6 +16,8 @@ namespace variations {
 
 namespace {
 
+const char kGroupTesting[] = "Testing";
+
 // The internal singleton accessor for the map, used to keep it thread-safe.
 class GroupMapAccessor {
  public:
@@ -252,6 +254,26 @@ std::string GetVariationParamValueByFeature(const base::Feature& feature,
 // They simply wrap existing functions in this file.
 namespace testing {
 
+VariationParamsManager::VariationParamsManager(
+    const std::string& trial_name,
+    const std::map<std::string, std::string>& params) {
+  SetVariationParams(trial_name, params);
+}
+
+VariationParamsManager::~VariationParamsManager() {
+  ClearAllVariationIDs();
+  ClearAllVariationParams();
+  field_trial_list_.reset();
+}
+
+void VariationParamsManager::SetVariationParams(
+    const std::string& trial_name,
+    const std::map<std::string, std::string>& params) {
+  field_trial_list_.reset(new base::FieldTrialList(nullptr));
+  variations::AssociateVariationParams(trial_name, kGroupTesting, params);
+  base::FieldTrialList::CreateFieldTrial(trial_name, kGroupTesting);
+}
+
 void ClearAllVariationIDs() {
   GroupMapAccessor::GetInstance()->ClearAllMapsForTesting();
 }