Implement Element.scrollIntoView for scroll-behavior: smooth.

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

Index: third_party/WebKit/Source/core/frame/RootFrameViewport.h
diff --git a/third_party/WebKit/Source/core/frame/RootFrameViewport.h b/third_party/WebKit/Source/core/frame/RootFrameViewport.h
index 661cda8f99283eca964bb9533b57f79f9053c816..a51113b3ffbdc8b0bea41532837e427b6eb90aa4 100644
--- a/third_party/WebKit/Source/core/frame/RootFrameViewport.h
+++ b/third_party/WebKit/Source/core/frame/RootFrameViewport.h
@@ -60,7 +60,8 @@ class CORE_EXPORT RootFrameViewport final
   LayoutRect ScrollIntoView(const LayoutRect& rect_in_content,
                             const ScrollAlignment& align_x,
                             const ScrollAlignment& align_y,
-                            ScrollType = kProgrammaticScroll) override;
+                            ScrollType = kProgrammaticScroll,
+                            bool is_smooth = false) override;
   IntRect VisibleContentRect(
       IncludeScrollbarsInRect = kExcludeScrollbars) const override;
   bool ShouldUseIntegerScrollOffset() const override;
@@ -79,6 +80,7 @@ class CORE_EXPORT RootFrameViewport final
   IntRect ScrollableAreaBoundingBox() const override;
   bool UserInputScrollable(ScrollbarOrientation) const override;
   bool ShouldPlaceVerticalScrollbarOnLeft() const override;
+  bool ScheduleAnimation() override;

[sunyunjia, 2017/05/12 18:40:25]

Not sure why this wasn't implemented. It was returning false and preventing the
viewport from scrolling

[bokan, 2017/05/15 17:15:27]

Acknowledged.

   void ScrollControlWasSetNeedsPaintInvalidation() override;
   GraphicsLayer* LayerForContainer() const override;
   GraphicsLayer* LayerForScrolling() const override;
@@ -94,6 +96,7 @@ class CORE_EXPORT RootFrameViewport final
   ScrollResult UserScroll(ScrollGranularity, const FloatSize&) override;
   bool ScrollAnimatorEnabled() const override;
   PlatformChromeClient* GetChromeClient() const override;
+  SmoothScrollSequencer* GetSmoothScrollSequencer() const override;
   void ServiceScrollAnimations(double) override;
   void UpdateCompositorScrollAnimations() override;
   void CancelProgrammaticScrollAnimation() override;