Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/platform/scroll/ScrollTypes.h

Index: third_party/WebKit/Source/platform/scroll/ScrollTypes.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollTypes.h b/third_party/WebKit/Source/platform/scroll/ScrollTypes.h
index 32d22c8071fd1e62bd29df498131f24396e2de42..1e40562b7a5b017832654326365f37d4d8e7ec75 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollTypes.h
+++ b/third_party/WebKit/Source/platform/scroll/ScrollTypes.h
@@ -207,6 +207,11 @@ enum ScrollBehavior {
   ScrollBehaviorSmooth,
 };
 
+enum ScrollBlock {
+  ScrollBlockStart,
+  ScrollBlockEnd,
+};
+
 // The result of an attempt to scroll. If didScroll is true, then
 // unusedScrollDelta gives the amount of the scroll delta that was not consumed
 // by scrolling.