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 927351b180e560cb47abba2e853a42cbb61d73b6..34dd098bdc7d6c88357a0b40647904f7294c90e6 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollTypes.h
+++ b/third_party/WebKit/Source/platform/scroll/ScrollTypes.h
@@ -211,6 +211,11 @@ 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.