Add variations params api to get params from features.

base/feature_list.cc

 // Copyright 2015 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.
 
 #include "base/feature_list.h"
 
 #include <stddef.h>
 
 #include <utility>
 #include <vector>
@@ skipping 119 matching lines @@
     }
   }
 }
 
 // static
 bool FeatureList::IsEnabled(const Feature& feature) {
   return GetInstance()->IsFeatureEnabled(feature);
 }
 
 // static
+FieldTrial* FeatureList::GetFieldTrial(const Feature& feature) {
+  return GetInstance()->GetAssociatedFieldTrial(feature);
+}
+
+// static
 std::vector<std::string> FeatureList::SplitFeatureListString(
     const std::string& input) {
   return SplitString(input, ",", TRIM_WHITESPACE, SPLIT_WANT_NONEMPTY);
 }
 
 // static
 bool FeatureList::InitializeInstance(const std::string& enable_features,
                                      const std::string& disable_features) {
   // We want to initialize a new instance here to support command-line features
   // in testing better. For example, we initialize a dummy instance in
@@ skipping 60 matching lines @@
     // TODO(asvitkine) Expand this section as more support is added.
 
     // If marked as OVERRIDE_USE_DEFAULT, simply return the default state below.
     if (entry.overridden_state != OVERRIDE_USE_DEFAULT)
       return entry.overridden_state == OVERRIDE_ENABLE_FEATURE;
   }
   // Otherwise, return the default state.
   return feature.default_state == FEATURE_ENABLED_BY_DEFAULT;
 }
 
+FieldTrial* FeatureList::GetAssociatedFieldTrial(const Feature& feature) {
+  DCHECK(initialized_);
+  DCHECK(IsValidFeatureOrFieldTrialName(feature.name)) << feature.name;
+  DCHECK(CheckFeatureIdentity(feature)) << feature.name;
+
+  auto it = overrides_.find(feature.name);
+  if (it != overrides_.end()) {
+    const OverrideEntry& entry = it->second;
+    return entry.field_trial;
+  }
+
+  return nullptr;
+}
+
 void FeatureList::RegisterOverridesFromCommandLine(
     const std::string& feature_list,
     OverrideState overridden_state) {
   for (const auto& value : SplitFeatureListString(feature_list)) {
     StringPiece feature_name(value);
     base::FieldTrial* trial = nullptr;
 
     // The entry may be of the form FeatureName<FieldTrialName - in which case,
     // this splits off the field trial name and associates it with the override.
     std::string::size_type pos = feature_name.find('<');
@@ skipping 39 matching lines @@
   return it->second == &feature;
 }
 
 FeatureList::OverrideEntry::OverrideEntry(OverrideState overridden_state,
                                           FieldTrial* field_trial)
     : overridden_state(overridden_state),
       field_trial(field_trial),
       overridden_by_field_trial(field_trial != nullptr) {}
 
 }  // namespace base