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 24e8029cd76195d5c3b2fcb13c43c455ff6dd9f9..77cf2704cf0221381a406af2b109ecb93f3e2efb 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
@@ -630,7 +630,8 @@ void LayoutBox::scrollRectToVisible(const LayoutRect& rect,
                                     const ScrollAlignment& alignX,
                                     const ScrollAlignment& alignY,
                                     ScrollType scrollType,
-                                    bool makeVisibleInVisualViewport) {
+                                    bool makeVisibleInVisualViewport,
+                                    ScrollBehavior scrollBehavior) {
   ASSERT(scrollType == ProgrammaticScroll || scrollType == UserScroll);
   // Presumably the same issue as in setScrollTop. See crbug.com/343132.
   DisableCompositingQueryAsserts disabler;
@@ -650,6 +651,13 @@ void LayoutBox::scrollRectToVisible(const LayoutRect& rect,
     restrictedByLineClamp = !containingBlock()->style()->lineClamp().isNone();
   }
 
+  ScrollBehavior behavior = ScrollBehaviorAuto;

[bokan, 2017/02/21 21:33:00]

This should be ScrollBehaviorInstant so that we pass either Smooth or Instant to
scrollIntoView. scrollIntoView should either DCHECK that it's not Auto or make
the param an isSmooth bool.

[sunyunjia, 2017/02/24 19:11:48]

Done.

+  if (scrollBehavior == ScrollBehaviorSmooth ||
+      (scrollBehavior == ScrollBehaviorAuto &&
+       style()->getScrollBehavior() == ScrollBehaviorSmooth)) {
+    behavior = ScrollBehaviorSmooth;
+  }
+
   if (hasOverflowClip() && !restrictedByLineClamp) {
     // Don't scroll to reveal an overflow layer that is restricted by the
     // -webkit-line-clamp property. This will prevent us from revealing text
@@ -657,7 +665,7 @@ void LayoutBox::scrollRectToVisible(const LayoutRect& rect,
     // TODO(eae): We probably don't need this any more as we don't share any
     //            code with the Safari RSS reeder.
     newRect = getScrollableArea()->scrollIntoView(rectToScroll, alignX, alignY,
-                                                  scrollType);
+                                                  scrollType, behavior);
     if (newRect.isEmpty())
       return;
   } else if (!parentBox && canBeProgramaticallyScrolled()) {
@@ -665,11 +673,11 @@ void LayoutBox::scrollRectToVisible(const LayoutRect& rect,
       HTMLFrameOwnerElement* ownerElement = document().localOwner();
       if (!isDisallowedAutoscroll(ownerElement, frameView)) {
         if (makeVisibleInVisualViewport) {
-          frameView->getScrollableArea()->scrollIntoView(rectToScroll, alignX,
-                                                         alignY, scrollType);
+          frameView->getScrollableArea()->scrollIntoView(
+              rectToScroll, alignX, alignY, scrollType, behavior);
         } else {
           frameView->layoutViewportScrollableArea()->scrollIntoView(
-              rectToScroll, alignX, alignY, scrollType);
+              rectToScroll, alignX, alignY, scrollType, behavior);
         }
         if (ownerElement && ownerElement->layoutObject()) {
           if (frameView->safeToPropagateScrollToParent()) {
@@ -699,9 +707,10 @@ void LayoutBox::scrollRectToVisible(const LayoutRect& rect,
   if (frame()->page()->autoscrollController().autoscrollInProgress())
     parentBox = enclosingScrollableBox();
 
-  if (parentBox)
+  if (parentBox) {
     parentBox->scrollRectToVisible(newRect, alignX, alignY, scrollType,
-                                   makeVisibleInVisualViewport);
+                                   makeVisibleInVisualViewport, scrollBehavior);
+  }
 }
 
 void LayoutBox::absoluteRects(Vector<IntRect>& rects,