Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/core/page/Page.h

Index: third_party/WebKit/Source/core/page/Page.h
diff --git a/third_party/WebKit/Source/core/page/Page.h b/third_party/WebKit/Source/core/page/Page.h
index 6258d19a4e9dd872fd5beada32ba55550bbdaf73..ccaea49b60b03068fd46c1032360ba34ddf107ae 100644
--- a/third_party/WebKit/Source/core/page/Page.h
+++ b/third_party/WebKit/Source/core/page/Page.h
@@ -67,6 +67,7 @@ class PluginData;
 class PointerLockController;
 class ScopedPageSuspender;
 class ScrollingCoordinator;
+class SmoothScrollSequencer;
 class Settings;
 class ConsoleMessageStorage;
 class SpellCheckerClient;
@@ -178,6 +179,8 @@ class CORE_EXPORT Page final : public GarbageCollectedFinalized<Page>,
 
   ScrollingCoordinator* GetScrollingCoordinator();
 
+  SmoothScrollSequencer* GetSmoothScrollSequencer();
+
   ClientRectList* NonFastScrollableRects(const LocalFrame*);
 
   Settings& GetSettings() const { return *settings_; }
@@ -310,6 +313,7 @@ class CORE_EXPORT Page final : public GarbageCollectedFinalized<Page>,
   const std::unique_ptr<PageScaleConstraintsSet> page_scale_constraints_set_;
   const Member<PointerLockController> pointer_lock_controller_;
   Member<ScrollingCoordinator> scrolling_coordinator_;
+  Member<SmoothScrollSequencer> smooth_scroll_sequencer_;
   const Member<BrowserControls> browser_controls_;
   const Member<ConsoleMessageStorage> console_message_storage_;
   const Member<EventHandlerRegistry> event_handler_registry_;