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 9809c865682ee30f0f302808ac88568905272c8d..343d5fd7cdbf6620dab5431f4955ff9a81aa807b 100644
--- a/third_party/WebKit/Source/platform/scroll/ProgrammaticScrollAnimator.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ProgrammaticScrollAnimator.cpp
@@ -10,6 +10,7 @@
 #include "platform/geometry/IntSize.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/scroll/ScrollableArea.h"
+#include "platform/scroll/SmoothScrollSequencer.h"
 #include "platform/wtf/PtrUtil.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebCompositorSupport.h"
@@ -76,6 +77,7 @@ void ProgrammaticScrollAnimator::tickAnimation(double monotonicTime) {
 
   if (isFinished) {
     m_runState = RunState::PostAnimationCleanup;
+    getScrollableArea()->getSmoothScrollSequencer()->notifyAnimationFinished();

[bokan, 2017/04/07 15:56:52]

What other programmatic animations is this class handling? We should make sure
we can distinguish between the ones that the sequencer needs to know about.

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

Done.

   } else if (!m_scrollableArea->scheduleAnimation()) {
     notifyOffsetChanged(offset);
     resetAnimationState();
@@ -168,6 +170,7 @@ void ProgrammaticScrollAnimator::notifyCompositorAnimationFinished(
     int groupId) {
   ASSERT(m_runState != RunState::RunningOnCompositorButNeedsUpdate);
   ScrollAnimatorCompositorCoordinator::compositorAnimationFinished(groupId);
+  getScrollableArea()->getSmoothScrollSequencer()->notifyAnimationFinished();
 }
 
 DEFINE_TRACE(ProgrammaticScrollAnimator) {