Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/core/frame/RootFrameViewport.cpp

Index: third_party/WebKit/Source/core/frame/RootFrameViewport.cpp
diff --git a/third_party/WebKit/Source/core/frame/RootFrameViewport.cpp b/third_party/WebKit/Source/core/frame/RootFrameViewport.cpp
index ee56bd1fe8fe55e8983f89a21f5b4af5215b71d5..53896c238112a3da6a8f1bbb9c46b60085b5c1ef 100644
--- a/third_party/WebKit/Source/core/frame/RootFrameViewport.cpp
+++ b/third_party/WebKit/Source/core/frame/RootFrameViewport.cpp
@@ -209,6 +209,7 @@ ScrollBehavior RootFrameViewport::ScrollBehaviorStyle() const {
 LayoutRect RootFrameViewport::ScrollIntoView(const LayoutRect& rect_in_content,
                                              const ScrollAlignment& align_x,
                                              const ScrollAlignment& align_y,
+                                             bool is_smooth,
                                              ScrollType scroll_type) {
   // We want to move the rect into the viewport that excludes the scrollbars so
   // we intersect the visual viewport with the scrollbar-excluded frameView
@@ -229,8 +230,13 @@ LayoutRect RootFrameViewport::ScrollIntoView(const LayoutRect& rect_in_content,
   LayoutRect target_viewport = ScrollAlignment::GetRectToExpose(
       view_rect_in_content, rect_in_content, align_x, align_y);
   if (target_viewport != view_rect_in_content) {
-    SetScrollOffset(ScrollOffset(target_viewport.X(), target_viewport.Y()),
-                    scroll_type);
+    ScrollOffset target_offset(target_viewport.X(), target_viewport.Y());
+    if (is_smooth) {
+      DCHECK(scroll_type == kProgrammaticScroll);
+      GetSmoothScrollSequencer()->QueueAnimation(this, target_offset);
+    } else {
+      SetScrollOffset(target_offset, scroll_type);
+    }
   }
 
   // RootFrameViewport only changes the viewport relative to the document so we
@@ -431,6 +437,10 @@ PlatformChromeClient* RootFrameViewport::GetChromeClient() const {
   return LayoutViewport().GetChromeClient();
 }
 
+SmoothScrollSequencer* RootFrameViewport::GetSmoothScrollSequencer() const {
+  return LayoutViewport().GetSmoothScrollSequencer();
+}
+
 void RootFrameViewport::ServiceScrollAnimations(double monotonic_time) {
   ScrollableArea::ServiceScrollAnimations(monotonic_time);
   LayoutViewport().ServiceScrollAnimations(monotonic_time);