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 b0a03cd8a8a1bbcf450bb1bfab2ac8676178243f..89ee7343345142c8240e058b25f37a54cd975b05 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
@@ -249,7 +249,8 @@ 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();