Expose scroll customization for touch to JS (behind REF).

Source/core/testing/Internals.h

Index: Source/core/testing/Internals.h
diff --git a/Source/core/testing/Internals.h b/Source/core/testing/Internals.h
index 7740770d16bc613c4aa3005896418a72cdde3dc3..8396dc3c968c91a97bf24cf8b7a31c9b92cc2527 100644
--- a/Source/core/testing/Internals.h
+++ b/Source/core/testing/Internals.h
@@ -346,7 +346,9 @@ public:
     void forcePluginPlaceholder(HTMLElement* plugin, PassRefPtrWillBeRawPtr<DocumentFragment>, ExceptionState&);
     void forcePluginPlaceholder(HTMLElement* plugin, const PluginPlaceholderOptions&, ExceptionState&);
 
-    // Scheudle a forced Blink GC run (Oilpan) at the end of event loop.
+    void setScrollChain(ScrollState*, const WillBeHeapVector<RefPtrWillBeMember<Element>>& elements, ExceptionState&);
+
+    // Schedule a forced Blink GC run (Oilpan) at the end of event loop.
     // Note: This is designed to be only used from PerformanceTests/BlinkGC to explicitly measure only Blink GC time.
     //       Normal LayoutTests should use gc() instead as it would trigger both Blink GC and V8 GC.
     void forceBlinkGCWithoutV8GC();