Preserve fractional scroll offset for JS scrolling API

Source/core/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 661 matching lines @@
         if (document().inQuirksMode())
             return;
 
         LocalFrame* frame = document().frame();
         if (!frame)
             return;
         FrameView* view = frame->view();
         if (!view)
             return;
 
-        view->setScrollPosition(IntPoint(roundf(newLeft * frame->pageZoomFactor()), view->scrollY()));
+        view->setScrollPosition(DoublePoint(newLeft * frame->pageZoomFactor(), view->scrollY()));
     }
 }
 
 void Element::setScrollLeft(const Dictionary& scrollOptionsHorizontal, ExceptionState& exceptionState)
 {
     String scrollBehaviorString;
     ScrollBehavior scrollBehavior = ScrollBehaviorAuto;
     if (DictionaryHelper::get(scrollOptionsHorizontal, "behavior", scrollBehaviorString)) {
         if (!ScrollableArea::scrollBehaviorFromString(scrollBehaviorString, scrollBehavior)) {
             exceptionState.throwTypeError("The ScrollBehavior provided is invalid.");
@@ skipping 25 matching lines @@
         if (document().inQuirksMode())
             return;
 
         LocalFrame* frame = document().frame();
         if (!frame)
             return;
         FrameView* view = frame->view();
         if (!view)
             return;
 
-        view->setScrollPosition(IntPoint(view->scrollX(), roundf(newTop * frame->pageZoomFactor())));
+        view->setScrollPosition(DoublePoint(view->scrollX(), newTop * frame->pageZoomFactor()));
     }
 }
 
 void Element::setScrollTop(const Dictionary& scrollOptionsVertical, ExceptionState& exceptionState)
 {
     String scrollBehaviorString;
     ScrollBehavior scrollBehavior = ScrollBehaviorAuto;
     if (DictionaryHelper::get(scrollOptionsVertical, "behavior", scrollBehaviorString)) {
         if (!ScrollableArea::scrollBehaviorFromString(scrollBehaviorString, scrollBehavior)) {
             exceptionState.throwTypeError("The ScrollBehavior provided is invalid.");
@@ skipping 2523 matching lines @@
         return wrapper;
 
     CustomElementBinding* binding = perContextData->customElementBinding(customElementDefinition());
 
     wrapper->SetPrototype(binding->prototype());
 
     return V8DOMWrapper::associateObjectWithWrapperNonTemplate(this, wrapperType, wrapper, isolate);
 }
 
 } // namespace blink