Use float for scroll offset.

third_party/WebKit/Source/web/ResizeViewportAnchor.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ResizeViewportAnchor_h
 #define ResizeViewportAnchor_h
 
 #include "core/page/Page.h"
-#include "platform/geometry/DoubleSize.h"
 #include "platform/heap/Handle.h"
+#include "platform/scroll/ScrollTypes.h"
 
 namespace blink {
 
 class FrameView;
 
 // This class scrolls the viewports to compensate for bounds clamping caused by
 // viewport size changes.
 //
 // It is needed when the layout viewport grows (causing its own scroll position
 // to be clamped) and also when it shrinks (causing the visual viewport's scroll
@@ skipping 23 matching lines @@
   DEFINE_INLINE_TRACE() { visitor->trace(m_page); }
 
  private:
   void beginScope() { m_scopeCount++; }
   void endScope();
   FrameView* rootFrameView();
 
   // The amount of resize-induced clamping drift accumulated during the
   // ResizeScope.  Note that this should NOT include other kinds of scrolling
   // that may occur during layout, such as from ScrollAnchor.
-  DoubleSize m_drift;
+  ScrollOffset m_drift;
   Member<Page> m_page;
   int m_scopeCount;
 };
 
 }  // namespace blink
 
 #endif  // ResizeViewportAnchor_h