Use float for scroll offset.

third_party/WebKit/Source/core/input/EventHandler.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 1723 matching lines @@
     int x = rightAligned ? firstRect.maxX() : firstRect.x();
     // In a multiline edit, firstRect.maxY() would endup on the next line, so -1.
     int y = firstRect.maxY() ? firstRect.maxY() - 1 : 0;
     locationInRootFrame = view->contentsToRootFrame(IntPoint(x, y));
   } else if (focusedElement) {
     IntRect clippedRect = focusedElement->boundsInViewport();
     locationInRootFrame =
         visualViewport.viewportToRootFrame(clippedRect.center());
   } else {
     locationInRootFrame = IntPoint(
-        rightAligned ? visualViewport.visibleRect().maxX() - kContextMenuMargin
-                     : visualViewport.location().x() + kContextMenuMargin,
-        visualViewport.location().y() + kContextMenuMargin);
+        rightAligned
+            ? visualViewport.visibleRect().maxX() - kContextMenuMargin
+            : visualViewport.scrollOffset().width() + kContextMenuMargin,
+        visualViewport.scrollOffset().height() + kContextMenuMargin);
   }
 
   m_frame->view()->setCursor(pointerCursor());
   IntPoint locationInViewport =
       visualViewport.rootFrameToViewport(locationInRootFrame);
   IntPoint globalPosition =
       view->getHostWindow()
           ->viewportToScreen(IntRect(locationInViewport, IntSize()),
                              m_frame->view())
           .location();
@@ skipping 235 matching lines @@
 
 
 FrameHost* EventHandler::frameHost() const {
   if (!m_frame->page())
     return nullptr;
 
   return &m_frame->page()->frameHost();
 }
 
 }  // namespace blink