[chrome://flags] Let features override params in the same trial

components/flags_ui/feature_entry_macros.h

 // 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.
 
 #ifndef COMPONENTS_FLAGS_UI_FEATURE_ENTRY_MACROS_H_
 #define COMPONENTS_FLAGS_UI_FEATURE_ENTRY_MACROS_H_
 
 #include "base/macros.h"
 
 // Macros to simplify specifying the type of FeatureEntry. Please refer to
@@ skipping 14 matching lines @@
   flags_ui::FeatureEntry::ENABLE_DISABLE_VALUE, enable_switch, enable_value, \
       disable_switch, disable_value, nullptr, 3, nullptr, nullptr, nullptr
 #define ENABLE_DISABLE_VALUE_TYPE(enable_switch, disable_switch) \
   ENABLE_DISABLE_VALUE_TYPE_AND_VALUE(enable_switch, "", disable_switch, "")
 #define MULTI_VALUE_TYPE(choices)                                          \
   flags_ui::FeatureEntry::MULTI_VALUE, nullptr, nullptr, nullptr, nullptr, \
       nullptr, arraysize(choices), choices, nullptr, nullptr
 #define FEATURE_VALUE_TYPE(feature)                                          \
   flags_ui::FeatureEntry::FEATURE_VALUE, nullptr, nullptr, nullptr, nullptr, \
       &feature, 3, nullptr, nullptr, nullptr
 #define FEATURE_WITH_VARIATIONS_VALUE_TYPE(feature, feature_variations,       \

[Alexei Svitkine (slow), 2017/02/24 16:18:20]

Separately, I think we should rename FEATURE_WITH_VARIATIONS to
FEATURE_WITH_PARAMS to make things more clear.

[jkrcal, 2017/02/27 08:04:36]

Makes sense. Can we postpone it to another CL and just add a TODO in this CL?

[Alexei Svitkine (slow), 2017/02/28 18:45:35]

Acknowledged.

[jkrcal, 2017/03/01 18:35:52]

Added a TODO.

                                            feature_trial)                     \
   flags_ui::FeatureEntry::FEATURE_WITH_VARIATIONS_VALUE, nullptr, nullptr,    \
       nullptr, nullptr, &feature, 3 + arraysize(feature_variations), nullptr, \
       feature_variations, feature_trial
+#define FEATURE_WITH_VARIATIONS_VALUE_TYPE_WITH_DEFAULT_TRIAL(                \
+    feature, feature_variations)                                              \
+  flags_ui::FeatureEntry::FEATURE_WITH_VARIATIONS_VALUE, nullptr, nullptr,    \
+      nullptr, nullptr, &feature, 3 + arraysize(feature_variations), nullptr, \
+      feature_variations, nullptr
 
 #endif  // COMPONENTS_FLAGS_UI_FEATURE_ENTRY_MACROS_H_