Use float for scroll offset.

third_party/WebKit/Source/core/events/MouseRelatedEvent.cpp

Index: third_party/WebKit/Source/core/events/MouseRelatedEvent.cpp
diff --git a/third_party/WebKit/Source/core/events/MouseRelatedEvent.cpp b/third_party/WebKit/Source/core/events/MouseRelatedEvent.cpp
index 837bdd6b1edfad5faa3059dcb72fa0fede56b2f1..36aaeb9f05ec8d13476e4c31308ee159a2e6b2f3 100644
--- a/third_party/WebKit/Source/core/events/MouseRelatedEvent.cpp
+++ b/third_party/WebKit/Source/core/events/MouseRelatedEvent.cpp
@@ -74,24 +74,24 @@ MouseRelatedEvent::MouseRelatedEvent(
       m_movementDelta(movementDelta),
       m_positionType(positionType) {
   LayoutPoint adjustedPageLocation;
-  LayoutPoint scrollPosition;
+  LayoutSize scrollOffset;
 
   LocalFrame* frame = view() && view()->isLocalDOMWindow()
                           ? toLocalDOMWindow(view())->frame()
                           : nullptr;
   if (frame && hasPosition()) {
     if (FrameView* frameView = frame->view()) {
-      scrollPosition = frameView->scrollPosition();
+      scrollOffset = LayoutSize(frameView->scrollOffsetInt());
       adjustedPageLocation = frameView->rootFrameToContents(rootFrameLocation);
       float scaleFactor = 1 / frame->pageZoomFactor();
       if (scaleFactor != 1.0f) {
         adjustedPageLocation.scale(scaleFactor, scaleFactor);
-        scrollPosition.scale(scaleFactor, scaleFactor);
+        scrollOffset.scale(scaleFactor, scaleFactor);
       }
     }
   }
 
-  m_clientLocation = adjustedPageLocation - toLayoutSize(scrollPosition);
+  m_clientLocation = adjustedPageLocation - scrollOffset;
   m_pageLocation = adjustedPageLocation;
 
   // Set up initial values for coordinates.