Implement Element.scrollIntoView for scroll-behavior: smooth.

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

Index: third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp
diff --git a/third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp b/third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp
index 1e6b1b694ac7b88a8a454348bce30302a726f0e7..3bd31655f9be5933d4e1b77f11d22baf6969634a 100644
--- a/third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp
+++ b/third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp
@@ -1210,6 +1210,21 @@ double LocalDOMWindow::devicePixelRatio() const {
   return GetFrame()->DevicePixelRatio();
 }
 
+void LocalDOMWindow::scrollViewportTo(ScrollableArea* viewport,
+                                      const ScrollOffset& offset,
+                                      ScrollBehavior scroll_behavior) const {
+  if (SmoothScrollSequencer* sequencer =
+          GetFrame()->GetPage()->GetSmoothScrollSequencer()) {
+    sequencer->AbortAnimations();
+    if (scroll_behavior == kScrollBehaviorSmooth) {
+      sequencer->QueueAnimation(viewport, offset);
+      sequencer->RunQueuedAnimations();
+    } else {
+      viewport->SetScrollOffset(offset, kProgrammaticScroll, scroll_behavior);
+    }
+  }
+}
+
 void LocalDOMWindow::scrollBy(double x,
                               double y,
                               ScrollBehavior scroll_behavior) const {
@@ -1237,8 +1252,7 @@ void LocalDOMWindow::scrollBy(double x,
   ScrollOffset scaled_delta(x * GetFrame()->PageZoomFactor(),
                             y * GetFrame()->PageZoomFactor());
 
-  viewport->SetScrollOffset(current_offset + scaled_delta, kProgrammaticScroll,
-                            scroll_behavior);
+  scrollViewportTo(viewport, current_offset + scaled_delta, scroll_behavior);
 }
 
 void LocalDOMWindow::scrollBy(const ScrollToOptions& scroll_to_options) const {
@@ -1279,8 +1293,7 @@ void LocalDOMWindow::scrollTo(double x, double y) const {
   ScrollableArea* viewport = page->GetSettings().GetInertVisualViewport()
                                  ? view->LayoutViewportScrollableArea()
                                  : view->GetScrollableArea();
-  viewport->SetScrollOffset(layout_offset, kProgrammaticScroll,
-                            kScrollBehaviorAuto);
+  scrollViewportTo(viewport, layout_offset, kScrollBehaviorAuto);
 }
 
 void LocalDOMWindow::scrollTo(const ScrollToOptions& scroll_to_options) const {
@@ -1327,8 +1340,7 @@ void LocalDOMWindow::scrollTo(const ScrollToOptions& scroll_to_options) const {
   ScrollableArea::ScrollBehaviorFromString(scroll_to_options.behavior(),
                                            scroll_behavior);
 
-  viewport->SetScrollOffset(ScrollOffset(scaled_x, scaled_y),
-                            kProgrammaticScroll, scroll_behavior);
+  scrollViewportTo(viewport, ScrollOffset(scaled_x, scaled_y), scroll_behavior);
 }
 
 void LocalDOMWindow::moveBy(int x, int y) const {