Clean-up the code for default variations in chrome://flags.

components/flags_ui/feature_entry.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 "components/flags_ui/feature_entry.h"
 
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "grit/components_strings.h"
@@ skipping 23 matching lines @@
     const int kEnableDisableDescriptionIds[] = {
         IDS_GENERIC_EXPERIMENT_CHOICE_DEFAULT,
         IDS_GENERIC_EXPERIMENT_CHOICE_ENABLED,
         IDS_GENERIC_EXPERIMENT_CHOICE_DISABLED,
     };
     description_id = kEnableDisableDescriptionIds[index];
   } else if (type == FeatureEntry::FEATURE_WITH_VARIATIONS_VALUE) {
     if (index == 0) {
       description_id = IDS_GENERIC_EXPERIMENT_CHOICE_DEFAULT;
     } else if (index == 1) {
-      // Variation 1: the default enabled variation => "Enabled".
       description_id = IDS_GENERIC_EXPERIMENT_CHOICE_ENABLED;
     } else if (index < num_options - 1) {
-      // Variations 2 .. n  => "Enabled <description_text>".
-      int variation_index = index - 1;
+      // First two options do not correspond to variations.

[Alexei Svitkine (slow), 2016/07/13 14:07:13]

Nit: I would actually rephrase this slightly, i.e. "do not have variations
params."

+      int variation_index = index - 2;
       return l10n_util::GetStringUTF16(IDS_GENERIC_EXPERIMENT_CHOICE_ENABLED) +
              base::ASCIIToUTF16(" ") +
              base::ASCIIToUTF16(
                  feature_variations[variation_index].description_text);
     } else {
       DCHECK_EQ(num_options - 1, index);
       description_id = IDS_GENERIC_EXPERIMENT_CHOICE_DISABLED;
     }
   } else {
     description_id = choices[index].description_id;
@@ skipping 20 matching lines @@
   else
     return FeatureEntry::FeatureState::ENABLED;
 }
 
 const FeatureEntry::FeatureVariation* FeatureEntry::VariationForOption(
     int index) const {
   DCHECK(type == FeatureEntry::FEATURE_VALUE ||
          type == FeatureEntry::FEATURE_WITH_VARIATIONS_VALUE);
   DCHECK_LT(index, num_options);
 
-  if (type == FeatureEntry::FEATURE_WITH_VARIATIONS_VALUE && index > 0 &&
+  if (type == FeatureEntry::FEATURE_WITH_VARIATIONS_VALUE && index > 1 &&
       index < num_options - 1) {
     // We have no variations for FEATURE_VALUE type. Option at |index|
-    // corresponds to variation at |index| - 1 as the first option is "Default".
-    return &feature_variations[index - 1];
+    // corresponds to variation at |index| - 2 as the list starts with "Default"
+    // and "Enabled" (with default parameters).
+    return &feature_variations[index - 2];
   }
   return nullptr;
 }
 
 namespace testing {
 
 // WARNING: '@' is also used in the html file. If you update this constant you
 // also need to update the html file.
 const char kMultiSeparator[] = "@";
 
 }  // namespace testing
 
 }  // namespace flags_ui