Build Fix for Use of undeclared identifier 'page'

rdar://125741072

Reviewed by Simon Fraser.

ASSERT(m_page); should be called rather than ASSERT(page());

* Source/WebCore/page/scrolling/AsyncScrollingCoordinator.cpp:
(WebCore::AsyncScrollingCoordinator::setScrollbarLayoutDirection):

Canonical link: https://commits.webkit.org/272448.847@safari-7618-branch

Source/WebCore/page/scrolling/AsyncScrollingCoordinator.cpp

@@ -375,7 +375,7 @@ void AsyncScrollingCoordinator::stopAnimatedScroll(ScrollableArea& scrollableAre
 void AsyncScrollingCoordinator::setScrollbarLayoutDirection(ScrollableArea& scrollableArea, UserInterfaceLayoutDirection scrollbarLayoutDirection)
 {
     ASSERT(isMainThread());
-    ASSERT(page());
+    ASSERT(m_page);
     auto scrollingNodeID = scrollableArea.scrollingNodeID();
     if (!scrollingNodeID)
         return;