Implement Element.scrollIntoView for scroll-behavior: smooth.

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

+// Copyright (c) 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+#ifndef SmoothScrollSequencer_h
+#define SmoothScrollSequencer_h
+
+#include <utility>
+#include <vector>
+#include "platform/scroll/ProgrammaticScrollAnimatorClient.h"
+#include "platform/scroll/ScrollTypes.h"
+
+namespace blink {
+
+class ScrollableArea;
+
+class PLATFORM_EXPORT SmoothScrollSequencer

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

Please add a class-level comment about what this class' purpose is (why we need
it) and what it does

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

Done.

+    : public ProgrammaticScrollAnimatorClient {
+ public:
+  static SmoothScrollSequencer* create();
+
+  ~SmoothScrollSequencer();
+
+  // Add a scroll offset animation to the back of a queue.
+  void queueAnimation(ScrollableArea*, ScrollOffset);
+
+  // Run the animation at the back of the queue and sets itself as a client
+  // of ProgrammaticScrollAnimator to receive finish notification.
+  void runQueuedAnimations();
+
+  // Pop the back of the queue and run the next animation in the queue.
+  void notifyAnimationFinished();
+
+  // Abort the currently running anmation and all the animations in the queue.
+  void abortAnimations();
+
+ protected:
+  explicit SmoothScrollSequencer();

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

There's no argument here so there's no implicit conversion possible. No need for
explicit.

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

Done.

+
+ private:
+  typedef std::pair<Member<ScrollableArea>, ScrollOffset> ScrollerAndOffsetPair;
+  std::vector<ScrollerAndOffsetPair> m_queue;
+};
+
+}  // namespace blink
+
+#endif  // SmoothScrollSequencer_h