Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/core/layout/LayoutBox.cpp

Index: third_party/WebKit/Source/core/layout/LayoutBox.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBox.cpp b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
index 5ac9de0dd96cd20cdc1b9a0df7524ce1bf754341..8a5b549ebe9ff9ae66b937e6e0549349861d9eed 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
@@ -645,7 +645,8 @@ void LayoutBox::ScrollRectToVisible(const LayoutRect& rect,
                                     const ScrollAlignment& align_x,
                                     const ScrollAlignment& align_y,
                                     ScrollType scroll_type,
-                                    bool make_visible_in_visual_viewport) {
+                                    bool make_visible_in_visual_viewport,
+                                    ScrollBehavior scroll_behavior) {
   DCHECK(scroll_type == kProgrammaticScroll || scroll_type == kUserScroll);
   // Presumably the same issue as in setScrollTop. See crbug.com/343132.
   DisableCompositingQueryAsserts disabler;
@@ -666,14 +667,21 @@ void LayoutBox::ScrollRectToVisible(const LayoutRect& rect,
         !ContainingBlock()->Style()->LineClamp().IsNone();
   }
 
+  bool is_smooth = false;
+  if (scroll_behavior == kScrollBehaviorSmooth ||
+      (scroll_behavior == kScrollBehaviorAuto &&
+       Style()->GetScrollBehavior() == kScrollBehaviorSmooth)) {
+    is_smooth = true;

[bokan, 2017/05/15 17:15:28]

This is another way of saying:

bool is_smooth = 
    scroll_behavior == kScrollBehaviorSmooth ||
        (scroll_behavior == kScrollBehaviorAuto && 
         Style()->GetScrollBehavior() == kScrollBehaviorSmooth);

[sunyunjia, 2017/05/19 16:24:29]

Done.

+  }
+
   if (HasOverflowClip() && !restricted_by_line_clamp) {
     // Don't scroll to reveal an overflow layer that is restricted by the
     // -webkit-line-clamp property. This will prevent us from revealing text
     // hidden by the slider in Safari RSS.
     // TODO(eae): We probably don't need this any more as we don't share any
     //            code with the Safari RSS reeder.
-    new_rect = GetScrollableArea()->ScrollIntoView(rect_to_scroll, align_x,
-                                                   align_y, scroll_type);
+    new_rect = GetScrollableArea()->ScrollIntoView(
+        rect_to_scroll, align_x, align_y, scroll_type, is_smooth);
     if (new_rect.IsEmpty())
       return;
   } else if (!parent_box && CanBeProgramaticallyScrolled()) {
@@ -682,10 +690,10 @@ void LayoutBox::ScrollRectToVisible(const LayoutRect& rect,
       if (!IsDisallowedAutoscroll(owner_element, frame_view)) {
         if (make_visible_in_visual_viewport) {
           frame_view->GetScrollableArea()->ScrollIntoView(
-              rect_to_scroll, align_x, align_y, scroll_type);
+              rect_to_scroll, align_x, align_y, scroll_type, is_smooth);
         } else {
           frame_view->LayoutViewportScrollableArea()->ScrollIntoView(
-              rect_to_scroll, align_x, align_y, scroll_type);
+              rect_to_scroll, align_x, align_y, scroll_type, is_smooth);
         }
         if (owner_element && owner_element->GetLayoutObject()) {
           if (frame_view->SafeToPropagateScrollToParent()) {
@@ -715,9 +723,11 @@ void LayoutBox::ScrollRectToVisible(const LayoutRect& rect,
   if (GetFrame()->GetPage()->GetAutoscrollController().AutoscrollInProgress())
     parent_box = EnclosingScrollableBox();
 
-  if (parent_box)
+  if (parent_box) {
     parent_box->ScrollRectToVisible(new_rect, align_x, align_y, scroll_type,
-                                    make_visible_in_visual_viewport);
+                                    make_visible_in_visual_viewport,
+                                    scroll_behavior);
+  }
 }
 
 void LayoutBox::AbsoluteRects(Vector<IntRect>& rects,