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 e644faaeae13ee25d1b711e89c2bf3f8853501fc..7bfb16447909a54e768545e01cf3f670e39382d3 100644
--- a/third_party/WebKit/Source/core/page/Page.h
+++ b/third_party/WebKit/Source/core/page/Page.h
@@ -66,6 +66,7 @@ class PluginData;
 class PointerLockController;
 class ScopedPageSuspender;
 class ScrollingCoordinator;
+class SmoothScrollSequencer;
 class Settings;
 class ConsoleMessageStorage;
 class SpellCheckerClient;
@@ -177,6 +178,8 @@ class CORE_EXPORT Page final : public GarbageCollectedFinalized<Page>,
 
   ScrollingCoordinator* GetScrollingCoordinator();
 
+  SmoothScrollSequencer* GetSmoothScrollSequencer();
+
   ClientRectList* NonFastScrollableRects(const LocalFrame*);
 
   Settings& GetSettings() const { return *settings_; }
@@ -302,6 +305,7 @@ 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_;