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

Source/core/testing/Internals.cpp

Index: Source/core/testing/Internals.cpp
diff --git a/Source/core/testing/Internals.cpp b/Source/core/testing/Internals.cpp
index 60a01a4e2f0013f89047e12ae3a2f6c53e14426c..4071a1a49f1695e73334e2d67e4865a94cc17986 100644
--- a/Source/core/testing/Internals.cpp
+++ b/Source/core/testing/Internals.cpp
@@ -115,6 +115,7 @@
 #include "core/page/NetworkStateNotifier.h"
 #include "core/page/Page.h"
 #include "core/page/PrintContext.h"
+#include "core/page/scrolling/ScrollState.h"
 #include "core/paint/DeprecatedPaintLayer.h"
 #include "core/plugins/testing/DictionaryPluginPlaceholder.h"
 #include "core/plugins/testing/DocumentFragmentPluginPlaceholder.h"
@@ -2406,6 +2407,15 @@ void Internals::forcePluginPlaceholder(HTMLElement* element, const PluginPlaceho
     toHTMLPlugInElement(element)->setPlaceholder(DictionaryPluginPlaceholder::create(element->document(), options));
 }
 
+void Internals::setScrollChain(
+    ScrollState* scrollState, const WillBeHeapVector<RefPtrWillBeMember<Element>>& elements, ExceptionState&)
+{
+    WillBeHeapDeque<RefPtrWillBeMember<Element>> scrollChain;
+    for (size_t i = 0; i < elements.size(); ++i)
+        scrollChain.append(elements[i]);
+    scrollState->setScrollChain(scrollChain);
+}
+
 void Internals::forceBlinkGCWithoutV8GC()
 {
     ThreadState::current()->setGCState(ThreadState::FullGCScheduled);