Convert the overlay scrollbar flag to use FeatureList

content/browser/site_per_process_browsertest.cc

Index: content/browser/site_per_process_browsertest.cc
diff --git a/content/browser/site_per_process_browsertest.cc b/content/browser/site_per_process_browsertest.cc
index cb7a479d278c1781ffa6b7d373b786eb0e27a4cf..76b29008237032c1c991a30a19416e8b48c6df88 100644
--- a/content/browser/site_per_process_browsertest.cc
+++ b/content/browser/site_per_process_browsertest.cc
@@ -15,6 +15,7 @@
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/command_line.h"
+#include "base/feature_list.h"
 #include "base/location.h"
 #include "base/memory/ptr_util.h"
 #include "base/path_service.h"
@@ -87,7 +88,7 @@
 #include "ui/events/event_utils.h"
 #include "ui/gfx/geometry/point.h"
 #include "ui/latency/latency_info.h"
-#include "ui/native_theme/native_theme_switches.h"
+#include "ui/native_theme/native_theme_features.h"
 
 #if defined(USE_AURA)
 #include "content/browser/renderer_host/render_widget_host_view_aura.h"
@@ -619,14 +620,25 @@ std::string SitePerProcessBrowserTest::DepictFrameTree(FrameTreeNode* node) {
 void SitePerProcessBrowserTest::SetUpCommandLine(
     base::CommandLine* command_line) {
   IsolateAllSitesForTesting(command_line);
+}
+
+void SitePerProcessBrowserTest::SetUpOnMainThread() {
 #if !defined(OS_ANDROID)
   // TODO(bokan): Needed for scrollability check in
   // FrameOwnerPropertiesPropagationScrolling. crbug.com/662196.
-  command_line->AppendSwitch(switches::kDisableOverlayScrollbar);
+  base::FeatureList* existing_feature_list = base::FeatureList::GetInstance();
+  if (existing_feature_list) {
+    std::string enabled_features;
+    std::string disabled_features;
+    base::FeatureList::GetInstance()->GetFeatureOverrides(&enabled_features,
+                                                          &disabled_features);
+    disabled_features += "," + std::string(features::kOverlayScrollbar.name);

[dtapuska, 2017/04/12 17:21:02]

How do you know disable_features actually has anything?

Would it make more sense to follow code like:
https://cs.chromium.org/chromium/src/components/subresource_filter/core/brows...

Where it initializes the scoped feature list from a feature list?

[chaopeng, 2017/04/12 20:23:15]

Can not make this work as the link.

+    feature_list_.InitFromCommandLine(enabled_features, disabled_features);
+  } else {
+    feature_list_.InitAndDisableFeature(features::kOverlayScrollbar);
+  }
 #endif
-};
 
-void SitePerProcessBrowserTest::SetUpOnMainThread() {
   host_resolver()->AddRule("*", "127.0.0.1");
   SetupCrossSiteRedirector(embedded_test_server());
   ASSERT_TRUE(embedded_test_server()->Start());