Implement Element.scrollIntoView for scroll-behavior: smooth.

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

Index: third_party/WebKit/Source/platform/scroll/SmoothScrollSequencer.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/SmoothScrollSequencer.cpp b/third_party/WebKit/Source/platform/scroll/SmoothScrollSequencer.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..b5ed3aada4a3c321a8746399a61491b6a8db0c36
--- /dev/null
+++ b/third_party/WebKit/Source/platform/scroll/SmoothScrollSequencer.cpp
@@ -0,0 +1,48 @@
+// 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.
+#include "platform/scroll/SmoothScrollSequencer.h"
+
+#include "platform/scroll/ProgrammaticScrollAnimator.h"
+#include "platform/scroll/ScrollableArea.h"
+
+namespace blink {
+
+SmoothScrollSequencer* SmoothScrollSequencer::Create() {
+  return new SmoothScrollSequencer();
+}
+
+SmoothScrollSequencer::SmoothScrollSequencer() {}
+
+void SmoothScrollSequencer::QueueAnimation(ScrollableArea* scrollable,
+                                           ScrollOffset offset) {
+  ScrollerAndOffsetPair scroller_offset(scrollable, offset);
+  queue_.push_back(scroller_offset);
+}
+
+void SmoothScrollSequencer::RunQueuedAnimations() {
+  if (queue_.empty()) {
+    current_scrollable_ = nullptr;
+    return;
+  }
+  ScrollerAndOffsetPair scroller_offset = queue_.back();
+  queue_.pop_back();
+  ScrollableArea* scrollable = scroller_offset.first;
+  current_scrollable_ = scrollable;
+  ScrollOffset offset = scroller_offset.second;
+  scrollable->GetProgrammaticScrollAnimator().AnimateToOffset(offset, true);
+}
+
+void SmoothScrollSequencer::AbortAnimations() {
+  if (current_scrollable_) {
+    current_scrollable_->GetProgrammaticScrollAnimator().CancelAnimation();
+    current_scrollable_ = nullptr;
+  }
+  queue_.clear();
+}
+
+DEFINE_TRACE(SmoothScrollSequencer) {

[bokan, 2017/05/19 18:37:14]

I think you'll also need to visit each ScrollableArea in the queue

[sunyunjia, 2017/05/19 22:30:41]

Acknowledged.

+  visitor->Trace(current_scrollable_);
+}
+
+}  // namespace blink