Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/platform/scroll/ScrollableArea.h

Index: third_party/WebKit/Source/platform/scroll/ScrollableArea.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollableArea.h b/third_party/WebKit/Source/platform/scroll/ScrollableArea.h
index f5f6a86dd3463eda42ea8a71a86622a9c72d28ce..3ce1f82b86dc7dd2e45f858157040c510f09e548 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollableArea.h
+++ b/third_party/WebKit/Source/platform/scroll/ScrollableArea.h
@@ -49,6 +49,7 @@ class LayoutBox;
 class LayoutObject;
 class PaintLayer;
 class ProgrammaticScrollAnimator;
+class ProgrammaticScrollCoordinator;
 struct ScrollAlignment;
 class ScrollAnchor;
 class ScrollAnimatorBase;
@@ -78,6 +79,11 @@ class PLATFORM_EXPORT ScrollableArea : public GarbageCollectedMixin {
   // coordinate space.
   virtual HostWindow* getHostWindow() const { return 0; }
 
+  virtual ProgrammaticScrollCoordinator* getProgrammaticScrollCoordinator()
+      const {
+    return 0;
+  }
+
   virtual ScrollResult userScroll(ScrollGranularity, const ScrollOffset&);
 
   virtual void setScrollOffset(const ScrollOffset&,
@@ -100,7 +106,8 @@ class PLATFORM_EXPORT ScrollableArea : public GarbageCollectedMixin {
   virtual LayoutRect scrollIntoView(const LayoutRect& rectInContent,
                                     const ScrollAlignment& alignX,
                                     const ScrollAlignment& alignY,
-                                    ScrollType = ProgrammaticScroll);
+                                    ScrollType = ProgrammaticScroll,
+                                    ScrollBehavior = ScrollBehaviorAuto);
 
   // Returns a rect, in the space of the area's backing graphics layer, that
   // contains the visual region of all scrollbar parts.