Implement Element.scrollIntoView for scroll-behavior: smooth.

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

Index: third_party/WebKit/Source/core/frame/FrameView.cpp
diff --git a/third_party/WebKit/Source/core/frame/FrameView.cpp b/third_party/WebKit/Source/core/frame/FrameView.cpp
index 8d4c481c736b66dee09a30ed0aea50f0701552ed..5f44a675024b89eb28d8d0dc642b81054f78b894 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -2147,6 +2147,13 @@ PlatformChromeClient* FrameView::GetChromeClient() const {
   return &page->GetChromeClient();
 }
 
+SmoothScrollSequencer* FrameView::GetSmoothScrollSequencer() const {
+  Page* page = GetFrame().GetPage();
+  if (!page)
+    return nullptr;
+  return page->GetSmoothScrollSequencer();
+}
+
 void FrameView::ContentsResized() {
   if (frame_->IsMainFrame() && frame_->GetDocument()) {
     if (TextAutosizer* text_autosizer =
@@ -4635,14 +4642,20 @@ bool FrameView::ShouldPlaceVerticalScrollbarOnLeft() const {
 LayoutRect FrameView::ScrollIntoView(const LayoutRect& rect_in_content,
                                      const ScrollAlignment& align_x,
                                      const ScrollAlignment& align_y,
-                                     ScrollType scroll_type) {
+                                     ScrollType scroll_type,
+                                     bool is_smooth) {
   LayoutRect view_rect(VisibleContentRect());
   LayoutRect expose_rect = ScrollAlignment::GetRectToExpose(
       view_rect, rect_in_content, align_x, align_y);
   if (expose_rect != view_rect) {
-    SetScrollOffset(
-        ScrollOffset(expose_rect.X().ToFloat(), expose_rect.Y().ToFloat()),
-        scroll_type);
+    ScrollOffset target_offset(expose_rect.X().ToFloat(),
+                               expose_rect.Y().ToFloat());
+    if (is_smooth) {
+      DCHECK(scroll_type != kUserScroll);
+      GetSmoothScrollSequencer()->QueueAnimation(this, target_offset);
+    } else {
+      SetScrollOffset(target_offset, scroll_type);
+    }
   }
 
   // Scrolling the FrameView cannot change the input rect's location relative to