Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp

Index: third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
diff --git a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
index b32feec3fc12bd33516f86f21e7ccee499324044..1a1f0cdf4ecdf3419f75746ef183da97b8ad70cf 100644
--- a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -105,6 +105,7 @@ DEFINE_TRACE(ScrollingCoordinator) {
   visitor->trace(m_page);
   visitor->trace(m_horizontalScrollbars);
   visitor->trace(m_verticalScrollbars);
+  visitor->trace(m_programmaticScrollCoordinator);
 }
 
 void ScrollingCoordinator::setShouldHandleScrollGestureOnMainThreadRegion(
@@ -1164,4 +1165,13 @@ bool ScrollingCoordinator::frameViewIsDirty() const {
   return false;
 }
 
+ProgrammaticScrollCoordinator*
+ScrollingCoordinator::programmaticScrollCoordinator() {
+  if (!m_programmaticScrollCoordinator) {
+    m_programmaticScrollCoordinator = ProgrammaticScrollCoordinator::create();
+  }
+
+  return m_programmaticScrollCoordinator.get();
+}
+
 }  // namespace blink