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 f84a9511e2fb7bb818b8f586b068041a4e5cf209..9cc7d9b4b4ab62b065f86cbc3b3b0efe9d595b9f 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& rectInContent,
                             const ScrollAlignment& alignX,
                             const ScrollAlignment& alignY,
-                            ScrollType = ProgrammaticScroll) override;
+                            ScrollType = ProgrammaticScroll,
+                            ScrollBehavior = ScrollBehaviorAuto) override;
   IntRect visibleContentRect(
       IncludeScrollbarsInRect = ExcludeScrollbars) const override;
   bool shouldUseIntegerScrollOffset() const override;
@@ -96,6 +97,8 @@ class CORE_EXPORT RootFrameViewport final
   ScrollResult userScroll(ScrollGranularity, const FloatSize&) override;
   bool scrollAnimatorEnabled() const override;
   HostWindow* getHostWindow() const override;
+  ProgrammaticScrollCoordinator* getProgrammaticScrollCoordinator()
+      const override;
   void serviceScrollAnimations(double) override;
   void updateCompositorScrollAnimations() override;
   void cancelProgrammaticScrollAnimation() override;