Init ScopedFeatureList with feature enabled status

The goal is to offer a shortcut for cases when tests may either
enable or disable a feature based on a condition.

Examples that could be simplified if such method exists:
 - https://cs.chromium.org/chromium/src/components/autofill/core/browser/form_structure_unittest.cc?l=50
 - https://cs.chromium.org/chromium/src/ui/app_list/views/search_result_page_view_unittest.cc?l=62

Change-Id: I408cae760aa6a031770498202eb817e3bbd63a6b
Reviewed-on: https://chromium-review.googlesource.com/1005421Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Fabio Tirelo <ftirelo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549704}

base/test/scoped_feature_list.cc

@@ -136,6 +136,15 @@ void ScopedFeatureList::InitAndDisableFeature(const Feature& feature) {
   InitWithFeaturesAndFieldTrials({}, {}, {feature});
 }
 
+void ScopedFeatureList::InitWithFeatureState(const Feature& feature,
+                                             bool enabled) {
+  if (enabled) {
+    InitAndEnableFeature(feature);
+  } else {
+    InitAndDisableFeature(feature);
+  }
+}
+
 void ScopedFeatureList::InitWithFeaturesAndFieldTrials(
     const std::vector<Feature>& enabled_features,
     const std::vector<FieldTrial*>& trials_for_enabled_features,

base/test/scoped_feature_list.h

@@ -83,6 +83,11 @@ class ScopedFeatureList final {
   // FeatureList and overridden with single disabled feature.
   void InitAndDisableFeature(const Feature& feature);
 
+  // Initializes and registers a FeatureList instance based on present
+  // FeatureList and overriden with a single feature either enabled or
+  // disabled depending on |enabled|.
+  void InitWithFeatureState(const Feature& feature, bool enabled);
+
  private:
   // Initializes and registers a FeatureList instance based on present
   // FeatureList and overridden with the given enabled and disabled features.