Convert the overlay scrollbar flag to use FeatureList

base/test/scoped_feature_list.cc

Index: base/test/scoped_feature_list.cc
diff --git a/base/test/scoped_feature_list.cc b/base/test/scoped_feature_list.cc
index f0f3f4edfba1f1d333ef3188836cf14273795739..68e6d4af9a5ed8f7855ece2775f87e639b4bb5fb 100644
--- a/base/test/scoped_feature_list.cc
+++ b/base/test/scoped_feature_list.cc
@@ -4,7 +4,12 @@
 
 #include "base/test/scoped_feature_list.h"
 
+#include <algorithm>
 #include <string>
+#include <vector>
+
+#include "base/strings/string_split.h"
+#include "base/strings/string_util.h"
 
 namespace base {
 namespace test {
@@ -70,5 +75,66 @@ void ScopedFeatureList::InitAndDisableFeature(const base::Feature& feature) {
   InitFromCommandLine(std::string(), feature.name);
 }
 
+void override_feature(const std::string& feature,

[dcheng, 2017/04/14 23:30:17]

Nit: OverrideFeature

[chaopeng, 2017/04/15 00:12:54]

Done.

+                      std::vector<std::string>& check_list,

[dcheng, 2017/04/14 23:30:17]

Output parameters in Chromium should pass by pointer, not mutable reference.

[chaopeng, 2017/04/15 00:12:54]

Done.

+                      std::vector<std::string>& add_to_list) {
+  // Start with * means use default.
+  if (StartsWith(feature, "*", CompareCase::SENSITIVE))
+    return;
+
+  // Remove field_trial info.
+  std::string feature_name = feature;
+  std::size_t index = feature_name.find("<");
+  if (index != std::string::npos)
+    feature_name = feature_name.substr(0, index);
+
+  if (std::any_of(
+          check_list.begin(), check_list.end(),
+          [&feature_name](std::string& s) { return s == feature_name; }))
+    return;
+
+  if (std::any_of(
+          add_to_list.begin(), add_to_list.end(),
+          [&feature_name](std::string& s) { return s == feature_name; }))
+    return;
+
+  add_to_list.push_back(feature_name);
+}
+
+void ScopedFeatureList::InitWithFeatureListAndOverrides(
+    base::FeatureList* feature_list,
+    const std::vector<std::string>& override_enabled_features,
+    const std::vector<std::string>& override_disabled_features) {
+  std::vector<std::string> merged_enabled_features(override_enabled_features);
+  std::vector<std::string> merged_disabled_features(override_disabled_features);
+
+  if (feature_list) {

[dcheng, 2017/04/14 23:30:17]

Why do we have to handle the null case? I'm also not sure why we plumb this in,
if we never use |feature_list| anyway and just consult
FeatureList::GetInstance()

[chaopeng, 2017/04/15 00:12:54]

For the null case, we just need to write the overrides to feature_list.

+    std::string enabled_features;
+    std::string disabled_features;
+    base::FeatureList::GetInstance()->GetFeatureOverrides(&enabled_features,
+                                                          &disabled_features);
+
+    std::vector<std::string> enabled_features_list = SplitString(

[dcheng, 2017/04/14 23:30:17]

How about SplitStringPiece?

+        enabled_features, ",", TRIM_WHITESPACE, SPLIT_WANT_NONEMPTY);
+
+    std::vector<std::string> disabled_features_list = SplitString(
+        disabled_features, ",", TRIM_WHITESPACE, SPLIT_WANT_NONEMPTY);
+
+    for (const std::string& feature : enabled_features_list) {
+      override_feature(feature, merged_disabled_features,
+                       merged_enabled_features);
+    }
+
+    for (const std::string& feature : disabled_features_list) {
+      override_feature(feature, merged_enabled_features,
+                       merged_disabled_features);
+    }
+  }
+
+  std::string enabled = JoinString(merged_enabled_features, ",");
+  std::string disabled = JoinString(merged_disabled_features, ",");
+  InitFromCommandLine(enabled, disabled);
+}
+
 }  // namespace test
 }  // namespace base