Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp

Index: third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp b/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
index af89b4faa00b1eb7369b3ab6a6d2b49b5089af2a..6a831b389e9591b8094c6624dd4e08e0f9225bbe 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
@@ -250,7 +250,8 @@ void ScrollableArea::userScrollHelper(const ScrollOffset& offset,
 LayoutRect ScrollableArea::scrollIntoView(const LayoutRect& rectInContent,
                                           const ScrollAlignment& alignX,
                                           const ScrollAlignment& alignY,
-                                          ScrollType) {
+                                          ScrollType,
+                                          bool isSmooth) {
   // TODO(bokan): This should really be implemented here but ScrollAlignment is
   // in Core which is a dependency violation.
   ASSERT_NOT_REACHED();