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 5c9cb1536b9d01af83ab5563da1dee09505ea885..9fc21a0360fc5ab8fc2eede350317f5f7975b592 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,
+                            bool isSmooth = false) override;
   IntRect visibleContentRect(
       IncludeScrollbarsInRect = ExcludeScrollbars) const override;
   bool shouldUseIntegerScrollOffset() const override;
@@ -92,6 +93,8 @@ 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;