Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/platform/scroll/ProgrammaticScrollAnimator.cpp

Index: third_party/WebKit/Source/platform/scroll/ProgrammaticScrollAnimator.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/ProgrammaticScrollAnimator.cpp b/third_party/WebKit/Source/platform/scroll/ProgrammaticScrollAnimator.cpp
index 8dd9110441daaab381ee5a5c87d571b7355d0461..13eb87f1b2677f69aa5d319291d89f93a2c91f99 100644
--- a/third_party/WebKit/Source/platform/scroll/ProgrammaticScrollAnimator.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ProgrammaticScrollAnimator.cpp
@@ -8,6 +8,7 @@
 #include "platform/animation/CompositorScrollOffsetAnimationCurve.h"
 #include "platform/geometry/IntSize.h"
 #include "platform/graphics/GraphicsLayer.h"
+#include "platform/scroll/ProgrammaticScrollCoordinator.h"
 #include "platform/scroll/ScrollableArea.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebCompositorSupport.h"
@@ -76,6 +77,9 @@ void ProgrammaticScrollAnimator::tickAnimation(double monotonicTime) {
 
   if (isFinished) {
     m_runState = RunState::PostAnimationCleanup;
+    getScrollableArea()
+        ->getProgrammaticScrollCoordinator()
+        ->notifyAnimationFinished();
   } else if (!m_scrollableArea->scheduleAnimation()) {
     notifyOffsetChanged(offset);
     resetAnimationState();