Convert scroll anchoring flag to runtime-enabled feature.

third_party/WebKit/Source/core/layout/ScrollAnchorTest.cpp

 // 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 "core/layout/ScrollAnchor.h"
 
 #include "core/layout/LayoutTestHelper.h"
 
 namespace blink {
 
-static void enableScrollAnchoring(Settings& settings)
-{
-    settings.setScrollAnchoringEnabled(true);
-}
-
 class ScrollAnchorTest : public RenderingTest {
-    FrameSettingOverrideFunction settingOverrider() const override { return enableScrollAnchoring; }
+public:
+    ScrollAnchorTest() { RuntimeEnabledFeatures::setScrollAnchoringEnabled(true); }
+    ~ScrollAnchorTest() { RuntimeEnabledFeatures::setScrollAnchoringEnabled(false); }
 };
 
 TEST_F(ScrollAnchorTest, Basic)
 {
     ScrollAnchor scrollAnchor(document().view()->layoutViewportScrollableArea());
     scrollAnchor.clear();
     EXPECT_EQ(nullptr, scrollAnchor.anchorObject());
 }
 }