Preserve fractional scroll offset for JS scrolling API

Source/core/frame/LocalDOMWindow.cpp

Index: Source/core/frame/LocalDOMWindow.cpp
diff --git a/Source/core/frame/LocalDOMWindow.cpp b/Source/core/frame/LocalDOMWindow.cpp
index e12dc74e4ff60ba089e28e435da0aa56f0f7715b..622a3947f175d5d0fbe4feeeffc0e5f4c7527c83 100644
--- a/Source/core/frame/LocalDOMWindow.cpp
+++ b/Source/core/frame/LocalDOMWindow.cpp
@@ -1360,7 +1360,7 @@ void LocalDOMWindow::scrollBy(double x, double y, ScrollBehavior scrollBehavior)
     if (!view)
         return;
 
-    IntSize scaledOffset(static_cast<int>(x * m_frame->pageZoomFactor()), static_cast<int>(y * m_frame->pageZoomFactor()));
+    DoubleSize scaledOffset(x * m_frame->pageZoomFactor(), y * m_frame->pageZoomFactor());
     view->scrollBy(scaledOffset, scrollBehavior);
 }
 
@@ -1383,7 +1383,7 @@ void LocalDOMWindow::scrollTo(double x, double y, ScrollBehavior scrollBehavior)
     if (!view)
         return;
 
-    IntPoint layoutPos(static_cast<int>(x * m_frame->pageZoomFactor()), static_cast<int>(y * m_frame->pageZoomFactor()));
+    DoublePoint layoutPos(x * m_frame->pageZoomFactor(), y * m_frame->pageZoomFactor());
     view->setScrollPosition(layoutPos, scrollBehavior);
 }