Preserve fractional scroll offset for JS scrolling API

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 1393 matching lines @@
     }
 
     LayoutRect bounds = element->boundingBox();
     int centeringOffsetX = (targetRect.width() - bounds.width()) / 2;
     int centeringOffsetY = (targetRect.height() - bounds.height()) / 2;
 
     IntPoint targetOffset(
         bounds.x() - centeringOffsetX - targetRect.x(),
         bounds.y() - centeringOffsetY - targetRect.y());
 
-    setScrollPosition(targetOffset);
+    setScrollPosition(DoublePoint(targetOffset));
 
     if (pinchVirtualViewportEnabled) {
         IntPoint remainder = IntPoint(targetOffset - scrollPosition());
         m_frame->page()->frameHost().pinchViewport().move(remainder);
     }
 }
 
-void FrameView::setScrollPosition(const IntPoint& scrollPoint, ScrollBehavior scrollBehavior)
+void FrameView::setScrollPosition(const DoublePoint& scrollPoint, ScrollBehavior scrollBehavior)
 {
     cancelProgrammaticScrollAnimation();
     TemporaryChange<bool> changeInProgrammaticScroll(m_inProgrammaticScroll, true);
     m_maintainScrollPositionAnchor = nullptr;
 
-    IntPoint newScrollPosition = adjustScrollPositionWithinRange(scrollPoint);
+    DoublePoint newScrollPosition = adjustScrollPositionWithinRange(scrollPoint);
 
-    if (newScrollPosition == scrollPosition())
+    if (newScrollPosition == scrollPositionDouble())
         return;
 
     if (scrollBehavior == ScrollBehaviorAuto) {
         RenderObject* renderer = m_frame->document()->documentElement() ? m_frame->document()->documentElement()->renderer() : 0;
         if (renderer)
             scrollBehavior = renderer->style()->scrollBehavior();
         else
             scrollBehavior = ScrollBehaviorInstant;
     }
     ScrollView::setScrollPosition(newScrollPosition, scrollBehavior);
@@ skipping 676 matching lines @@
         return IntRect();
     return page->chrome().windowResizerRect();
 }
 
 void FrameView::setVisibleContentScaleFactor(float visibleContentScaleFactor)
 {
     if (m_visibleContentScaleFactor == visibleContentScaleFactor)
         return;
 
     m_visibleContentScaleFactor = visibleContentScaleFactor;
-    updateScrollbars(scrollOffset());
+    updateScrollbars(scrollOffsetDouble());
 }
 
 void FrameView::setInputEventsTransformForEmulation(const IntSize& offset, float contentScaleFactor)
 {
     m_inputEventsOffsetForEmulation = offset;
     m_inputEventsScaleFactorForEmulation = contentScaleFactor;
 }
 
 IntSize FrameView::inputEventsOffsetForEmulation() const
 {
@@ skipping 893 matching lines @@
     IntSize visibleSize = expandedIntSize(visibleContentSizeF);
 
     IntPoint maximumOffset(
         contentsWidth() - visibleSize.width() - scrollOrigin().x(),
         contentsHeight() - visibleSize.height() - scrollOrigin().y());
     maximumOffset.clampNegativeToZero();
     return maximumOffset;
 }
 
 } // namespace blink